Zoom optical system, imaging device and method for manufacturing the zoom optical system

ABSTRACT

A zoom optical system includes, disposed in order from an object, a first lens group (G 1 ) having positive refractive power, a second lens group (G 2 ) having negative refractive power, and a third lens group (G 3 ) having positive refractive power, wherein at least a part of the second lens group (G 2 ) or at least a part of the third lens group (G 3 ) is configured to be movable, as a vibration-proofing lens group for correcting an image blur, so as to have a movement component in a direction perpendicular to an optical axis, and the following conditional expression is satisfied:
 
4.40&lt; f 1/(− f 2)&lt;8.00
 
where f1 denotes a focal length of the first lens group (G 1 ), and f2 denotes a focal length of the second lens group (G 2 ).

TECHNICAL FIELD

The present invention relates to a zoom optical system, an imagingdevice, and a method for manufacturing the zoom optical system.

TECHNICAL BACKGROUND

Proposals have so far been made on zoom optical systems suitable forphotographic cameras, electronic still cameras, video cameras, and thelike (for example, see Patent Documents 1 and 2).

PRIOR ARTS LIST Patent Document

Patent Document 1: Japanese Laid-Open Patent Publication No.2012-42557(A)

Patent Document 2: Japanese Laid-Open Patent Publication No.S63-298210(A)

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, a conventional zoom optical system has faced a problem of largevariations in aberration upon zooming. Moreover, in order to achievehigher image quality, the system is desired to have an image blurcorrection mechanism for correcting an image blur caused by camerashake, or the like.

Moreover, the conventional zoom optical system has faced problems oflarge variations in aberration upon zooming and large variations inaberration upon focusing on a short distance object.

Moreover, a zoom optical system having further successful opticalperformance has been recently required.

Means to Solve the Problems

A zoom optical system according to a first aspect of the invention isformed of, disposed in order from an object, a first lens group havingpositive refractive power, a second lens group having negativerefractive power, and a third lens group having positive refractivepower, in which at least a part of the second lens group or at least apart of the third lens group is configured to be movable, as avibration-proof lens group for correcting an image blur, so as to have acomponent in a direction perpendicular to an optical axis, and thefollowing conditional expression is satisfied:4.40<f1/(−f2)<8.00

where f1 denotes a focal length of the first lens group, and

f2 denotes a focal length of the second lens group.

An imaging device according to a first aspect of the invention isprovided with the zooming optical system according to the first aspectof the invention.

A zoom optical system according to a second aspect of the invention has,disposed in order from an object, a first lens group having positiverefractive power, a second lens group having negative refractive power,and a third lens group having positive refractive power, in which atleast a part of the second lens group or at least a part of the thirdlens group is configured to be moveable, as a vibration-proof lens groupfor correcting an image blur, so as to have a component in a directionperpendicular to an optical axis, and the following conditionalexpression is satisfied:3.60<f1/f3<8.00

where f1 denotes a focal length of the first lens group, and

f3 denotes a focal length of the third lens group.

An imaging device according to a second aspect of the invention isprovided with the zooming optical system according to the second aspectof the invention.

A zoom optical system according to a third aspect of the invention isformed of, disposed in order from an object, a first lens group havingpositive refractive power, a second lens group having negativerefractive power, and a third lens group having positive refractivepower, in which, upon zooming from a wide-angle end state to a telephotoend state, focusing is made by moving the first lens group to adirection of the object along an optical axis direction and moving atleast a part of the third lens group along the optical axis direction,and the following conditional expression is satisfied:0.73<(−f2)/f3<2.00

where f2 denotes a focal length of the second lens group, and

f3 denotes a focal length of the third lens group.

An imaging device according to a third aspect of the invention isprovided with the zooming optical system according to the third aspectof the invention.

A zoom optical system according to a fourth aspect of the invention has,disposed in order from an object, a first lens group having positiverefractive power, a second lens group having negative refractive power,and a third lens group having positive refractive power, in which, uponzooming from a wide-angle end state to a telephoto end state, the firstlens group is moved to a direction of the object along an optical axisdirection, and the following conditional expressions are satisfied:0.14<fw/f1<0.260.77<fw/f3<1.05

where fw denotes a focal length of the zoom optical system in thewide-angle end state,

f1 denotes a focal length of the first lens group, and

f3 denotes a focal length of the third lens group.

An imaging device according to a fourth aspect of the invention isprovided with the zooming optical system according to the fourth aspectof the invention.

A zoom optical system according to a fifth aspect of the invention has,disposed in order from an object, a first lens group having positiverefractive power, a second lens group having negative refractive power,and a third lens group having positive refractive power, in whichfocusing is made by moving at least a part of the third lens group alongan optical axis direction, and the following conditional expression issatisfied:0.90<f3/fw<1.50

where f3 denotes a focal length of the third lens group, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

An imaging device according to a fifth aspect of the invention isprovided with the zooming optical system according to the fifth aspectof the invention.

A zoom optical system according to a sixth aspect of the invention has,disposed in order from an object, a first lens group having positiverefractive power, a second lens group having negative refractive power,and a third lens group having positive refractive power, in which atleast a part of the third lens group is configured to be movable, as avibration-proof lens group for correcting an image blur, so as to have acomponent in a direction perpendicular to an optical axis, and thefollowing conditional expression is satisfied:0.60<f3/fw<3.50

where f3 denotes a focal length of the third lens group, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

An imaging device according to a sixth aspect of the invention isprovided with the zooming optical system according to the sixth aspectof the invention.

A method for manufacturing a zoom optical system according to a firstaspect of the invention refers to the method including, disposed inorder from an object, a first lens group having positive refractivepower, a second lens group having negative refractive power, and a thirdlens group having positive refractive power, in which each lens isarranged within a lens barrel in such a manner that at least a part ofthe second lens group or at least a part of the third lens group isconfigured to be movable, as a vibration-proof lens group for correctingan image blur, so as to have a component in a direction perpendicular toan optical axis, and the following expression is satisfied:4.40<f1/(−f2)<8.00

where f1 denotes a focal length of the first lens group, and

f2 denotes a focal length of the second lens group.

A method for manufacturing a zoom optical system according to a secondaspect of the invention refers to the method including, disposed inorder from an object, a first lens group having positive refractivepower, a second lens group having negative refractive power, and a thirdlens group having positive refractive power, in which each lens isarranged within a lens barrel in such a manner that at least a part ofthe second lens group or at least a part of the third lens group isconfigured to be movable, as a vibration-proof lens group for correctingan image blur, so as to have a component in a direction perpendicular toan optical axis, and the following expression is satisfied:3.60<f1/f3<8.00

where f1 denotes a focal length of the first lens group, and

f3 denotes a focal length of the third lens group.

A method for producing a zoom optical system according to a third aspectof the invention refers to the method including, disposed in order froman object, a first lens group having positive refractive power, a secondlens group having negative refractive power, and a third lens grouphaving negative refractive power, in which each lens is arranged withina lens barrel in such a manner that, upon zooming from a wide-angle endstate to a telephoto end state, focusing is made by moving the firstlens group to a direction of the object along an optical axis direction,and moving at least a part of the lens group along the optical axisdirection, and the following expression is satisfied:0.73<(−f2)/f3<2.00

where f2 denotes a focal length of the second lens group, and

f3 denotes a focal length of the third lens group.

A method for producing a zoom optical system according to a fourthaspect of the invention refers to the method including, disposed inorder from an object, a first lens group having positive refractivepower, a second lens group having negative refractive power, and a thirdlens group having negative refractive power, in which each lens isarranged within a lens barrel in such a manner that, upon zooming from awide-angle end state to a telephoto end state, the first lens group ismoved to a direction of the object along an optical axis direction, andthe following expressions are satisfied:0.14<fw/f1<0.260.77<fw/f3<1.05

where fw denotes a focal length of the zoom optical system in thewide-angle end state,

f1 denotes a focal length of the first lens group, and

f3 denotes a focal length of the third lens group.

A method for manufacturing a zoom optical system according to a fifthaspect of the invention refers to the method including, disposed inorder from an object, a first lens group having positive refractivepower, a second lens group having negative refractive power, and a thirdlens group having positive refractive power, in which each lens isarranged within a lens barrel in such a manner that focusing is made bymoving at least a part of the third lens group along an optical axisdirection, and the following expression is satisfied:0.90<f3/fw<1.50

where f3 denotes a focal length of the third lens group, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

A method for manufacturing a zoom optical system according to a sixthaspect of the invention refers to the method having, disposed in orderfrom an object, a first lens group having positive refractive power, asecond lens group having negative refractive power, and a third lensgroup having positive refractive power, in which each lens is arrangedwithin a lens barrel in such a manner that at least a part of the thirdlens group is configured to be movable, as a vibration-proof lens groupfor correcting an image blur, so as to have a component in a directionperpendicular to an optical axis, and the following expression issatisfied:0.60<f3/fw<3.50

where f3 denotes a focal length of the third lens group, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a lens configuration of a zoomoptical system according to Example 1.

FIGS. 2A, 2B and 2C are graphs showing aberrations of the zoom opticalsystem (according to Example 1) in a wide-angle end state (f=18.500), inwhich FIG. 2A is graphs showing various aberrations upon focusing oninfinity, FIG. 2B is graphs showing various aberrations upon focusing ona short distant object (imaging magnification β=−0.0196), and FIG. 2C isgraphs showing coma aberration when an image blur is corrected (acorrection angle θ=0.30°) upon focusing on infinity.

FIGS. 3A, 3B and 3C are graphs showing aberrations of the zoom opticalsystem (according to Example 1) in an intermediate focal length state(f=35.000), in which FIG. 3A is graphs showing various aberrations uponfocusing on infinity, FIG. 3B is graphs showing various aberrations uponfocusing on a short distant object (imaging magnification β=−0.0365),and FIG. 3C is graphs showing coma aberration when an image blur iscorrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 4A, 4B and 4C are graphs showing aberrations of the zoom opticalsystem (according to Example 1) in a telephoto end state (f=53.500), inwhich FIG. 4A is graphs showing various aberrations upon focusing oninfinity, FIG. 4B is graphs showing various aberrations upon focusing ona short distant object (imaging magnification β=−0.0554), and FIG. 4C isgraphs showing coma aberration when an image blur is corrected (acorrection angle θ=0.30°) upon focusing on infinity.

FIG. 5 is a cross-sectional view showing a lens configuration of a zoomoptical system according to Example 2.

FIGS. 6A, 6B and 6C are graphs showing aberrations of the zoom opticalsystem (according to Example 2) in a wide-angle end state (f=18.500), inwhich FIG. 6A is graphs showing various aberrations upon focusing oninfinity, FIG. 6B is graphs showing various aberrations upon focusing ona short distant object (imaging magnification β=−0.0196), and FIG. 6C isgraphs showing coma aberration when an image blur is corrected (acorrection angle θ=0.30°) upon focusing on infinity.

FIGS. 7A, 7B and 7C are graphs showing aberrations of the zoom opticalsystem (according to Example 2) in an intermediate focal length state(f=34.176), in which FIG. 7A is graphs showing various aberrations uponfocusing on infinity, FIG. 7B is graphs showing various aberrations uponfocusing on a short distant object (imaging magnification β=−0.0358),and FIG. 7C is graphs showing coma aberration when an image blur iscorrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 8A, 8B and 8C are graphs showing aberrations of the zoom opticalsystem (according to Example 2) in a telephoto end state (f=53.500), inwhich FIG. 8A is graphs showing various aberrations upon focusing oninfinity, FIG. 8B is graphs showing various aberrations upon focusing ona short distant object (imaging magnification β=−0.0556), and FIG. 8C isgraphs showing coma aberration when an image blur is corrected (acorrection angle θ=0.30°) upon focusing on infinity.

FIG. 9 is a cross-sectional view showing a lens configuration of a zoomoptical system according to Example 3.

FIGS. 10A, 10B and 10C are graphs showing aberrations of the zoomoptical system (according to Example 3) in a wide-angle end state(f=18.477), in which FIG. 10A is graphs showing various aberrations uponfocusing on infinity, FIG. 10B is graphs showing various aberrationsupon focusing on a short distant object (imaging magnificationβ=−0.0194), and FIG. 10C is graphs showing coma aberration when an imageblur is corrected (a correction angle θ=0.30°) upon focusing oninfinity.

FIGS. 11A, 11B and 11C are graphs showing aberrations of the zoomoptical system (according to Example 3) in an intermediate focal lengthstate (f=34.000), in which FIG. 11A is graphs showing variousaberrations upon focusing on infinity, FIG. 11B is graphs showingvarious aberrations upon focusing on a short distant object (imagingmagnification β=−0.0355), and FIG. 11C is graphs showing coma aberrationwhen an image blur is corrected (a correction angle θ=30°) upon focusingon infinity.

FIGS. 12A, 12B and 12C are graphs showing aberrations of the zoomoptical system (according to Example 3) in a telephoto end state(f=53.500), in which FIG. 12A is graphs showing various aberrations uponfocusing on infinity, FIG. 12B is graphs showing various aberrationsupon focusing on a short distant object (imaging magnificationβ=−0.0552), and FIG. 12C is graphs showing coma aberration when an imageblur is corrected (a correction angle θ=0.30°) upon focusing oninfinity.

FIG. 13 is a cross-sectional view showing a lens configuration of a zoomoptical system according to Example 4.

FIGS. 14A, 14B and 14C are graphs showing aberrations of the zoomoptical system (according to Example 4) in a wide-angle end state(f=18.500), in which FIG. 14A is graphs showing various aberrations uponfocusing on infinity, FIG. 14B is graphs showing various aberrationsupon focusing on a short distant object (imaging magnificationβ=−0.0194), and FIG. 14C is graphs showing coma aberration when an imageblur is corrected (a correction angle θ=0.30°) upon focusing oninfinity.

FIGS. 15A, 15B and 15C are graphs showing aberrations of the zoomoptical system (according to Example 4) in an intermediate focal lengthstate (f=34.061), in which FIG. 15A is graphs showing variousaberrations upon focusing on infinity, FIG. 15B is graphs showingvarious aberrations upon focusing on a short distant object (imagingmagnification β=−0.0355), and FIG. 15C is graphs showing coma aberrationwhen an image blur is corrected (a correction angle θ=30°) upon focusingon infinity.

FIGS. 16A, 16B and 16C are graphs showing aberrations of the zoomoptical system (according to Example 4) in a telephoto end state(f=53.500), in which FIG. 16A is graphs showing various aberrations uponfocusing on infinity, FIG. 16B is graphs showing various aberrationsupon focusing on a short distant object (imaging magnificationβ=−0.0556), and FIG. 16C is graphs showing coma aberration when an imageblur is corrected (a correction angle θ=0.30°) upon focusing oninfinity.

FIG. 17 is a substantial cross-sectional view showing a configuration ofa camera according to each of first to fourth embodiments.

FIG. 18 is a flowchart for describing a method for manufacturing thezoom optical system according to the first embodiment.

FIG. 19 is a flowchart for describing a method for manufacturing thezoom optical system according to the second embodiment.

FIG. 20 is a flowchart for describing a method for manufacturing thezoom optical system according to the third embodiment.

FIG. 21 is a flowchart for describing a method for manufacturing thezoom optical system according to the fourth embodiment.

FIG. 22 is a cross-sectional view showing a lens configuration of a zoomoptical system according to Example 5.

FIGS. 23A, 23B and 23C are graphs showing aberrations of the zoomoptical system (according to Example 5) in a wide-angle end state(f=18.50), in which FIG. 23A is graphs showing various aberrations uponfocusing on infinity, FIG. 23B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 23C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.009).

FIGS. 24A, 24B and 24C are graphs showing aberrations of the zoomoptical system (according to Example 5) in an intermediate focal lengthstate (f=34.95), in which FIG. 24A is graphs showing various aberrationsupon focusing on infinity, FIG. 24B is graphs showing coma aberrationwhen an image blur is corrected (a vibration-proof lens group shiftamount=0.2 mm) upon focusing on infinity, and FIG. 24C is graphs showingvarious aberrations upon focusing on a short distant object (imagingmagnification β=−0.018).

FIGS. 25A, 25B and 25C are graphs showing aberrations of the zoomoptical system (according to Example 5) in a telephoto end state(f=53.50), in which FIG. 25A is graphs showing various aberrations uponfocusing on infinity, FIG. 25B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 25C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.027).

FIG. 26 is a cross-sectional view showing a lens configuration of a zoomoptical system according to Example 6.

FIGS. 27A, 27B and 27C are graphs showing aberrations of the zoomoptical system (according to Example 6) in a wide-angle end state(f=18.74), in which FIG. 27A is graphs showing various aberrations uponfocusing on infinity, FIG. 27B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 27C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.010).

FIGS. 28A, 28B and 28C are graphs showing aberrations of the zoomoptical system (according to Example 6) in an intermediate focal lengthstate (f=34.50), in which FIG. 28A is graphs showing various aberrationsupon focusing on infinity, FIG. 28B is graphs showing coma aberrationwhen an image blur is corrected (a vibration-proof lens group shiftamount=0.2 mm) upon focusing on infinity, and FIG. 28C is graphs showingvarious aberrations upon focusing on a short distant object (imagingmagnification β=−0.018).

FIGS. 29A, 29B and 29C are graphs showing aberrations of the zoomoptical system (according to Example 6) in a telephoto end state(f=52.08), in which FIG. 29A is graphs showing various aberrations uponfocusing on infinity, FIG. 29B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 29C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.026).

FIG. 30 is a cross-sectional view showing a lens configuration of a zoomoptical system according to Example 7.

FIGS. 31A, 31B and 31C are graphs showing aberrations of the zoomoptical system (according to Example 7) in a wide-angle end state(f=18.72), in which FIG. 31A is graphs showing various aberrations uponfocusing on infinity, FIG. 31B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 31C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.010).

FIGS. 32A, 32B and 32C are graphs showing aberrations of the zoomoptical system (according to Example 7) in an intermediate focal lengthstate (f=35.50), in which FIG. 32A is graphs showing various aberrationsupon focusing on infinity, FIG. 32B is graphs showing coma aberrationwhen an image blur is corrected (a vibration-proof lens group shiftamount=0.2 mm) upon focusing on infinity, and FIG. 32C is graphs showingvarious aberrations upon focusing on a short distant object (imagingmagnification β=−0.018).

FIGS. 33A, 33B and 33C are graphs showing aberrations of the zoomoptical system (according to Example 7) in a telephoto end state(f=52.00), in which FIG. 33A is graphs showing various aberrations uponfocusing on infinity, FIG. 33B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 33C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.027).

FIG. 34 is a substantial cross-sectional view showing a configuration ofa camera according to each of fifth and sixth embodiments.

FIG. 35 is a flowchart for describing a method for manufacturing thezoom optical system according to the fifth embodiment.

FIG. 36 is a flowchart for describing a method for manufacturing thezoom optical system according to the sixth embodiment.

DESCRIPTION OF THE EMBODIMENTS (FIRST TO FOURTH EMBODIMENTS)

Hereinafter, a first embodiment will be described with reference todrawings. As shown in FIG. 1, a zoom optical system ZL according to thefirst embodiment is formed of, disposed in order from an object, a firstlens group G1 having positive refractive power, a second lens group G2having negative refractive power, and a third lens group G3 havingpositive refractive power.

According to this configuration, size reduction of a lens barrel andsecurement of a sufficient zoom ratio in a wide-angle end state can beachieved.

In the zoom optical system ZL according to the first embodiment, atleast a part of the second lens group G2 or at least a part of the thirdlens group G3 is configured to be movable, as a vibration-proof lensgroup for correcting an image blur, so as to have a component in adirection perpendicular to an optical axis.

According to this configuration, size reduction of an image blurcorrection mechanism including the vibration-proof lens group can beachieved.

Then, under the configuration, the following conditional expression (1)is satisfied:4.40<f1/(−f2)<8.00  (1)

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

The conditional expression (1) specifies a proper ratio of the focallength of the first lens group G1 to the focal length of the second lensgroup G2. Successful optical performance and size reduction of anoptical system can be achieved by satisfying the conditional expression(1).

If the ratio thereof is less than a lower limit of the conditionalexpression (1), refractive power of the first lens group G1 increases,and correction of coma aberration, astigmatism, and curvature of fieldin a telephoto end state becomes difficult, and therefore such a case isnot preferable.

An effect of the first embodiment can be ensured by setting the lowerlimit of the conditional expression (1) to 5.00.

If the ratio thereof is more than an upper limit of the conditionalexpression (1), refractive power of the second lens group G2 increases,correction of coma aberration and astigmatism in a wide-angle end statebecomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the upperlimit of the conditional expression (1) to 7.00.

In the zoom optical system ZL according to the first embodiment, zoomingis preferably made by varying an air distance between the first lensgroup G1 and the second lens group G2 and an air distance between thesecond lens group G2 and the third lens group G3.

According to this configuration, while variations in sphericalaberration and curvature of field upon zooming are suppressed, asufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the first embodiment, thethird lens group G3 is formed of, disposed in order from an object, a31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33,in which the 32nd lens group G32 is preferably configured to be movable,as the vibration-proof lens group, so as to have a component in adirection perpendicular to an optical axis.

According to this configuration, successful optical performance can berealized upon correcting the image blur (vibration proofing). Sizereduction of the image blur correction mechanism can also be achieved.

In the zoom optical system ZL according to the first embodiment, the32nd lens group G32 preferably has negative refractive power.

According to this configuration, successful optical performance can berealized upon correcting the image blur (vibration proofing).

The zoom optical system ZL according to the first embodiment preferablysatisfies the following conditional expression (2):2.00<(−f32)/f3<6.00  (2)

where f32 denotes a focal length of the 32nd lens group G32, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (2) specifies a proper ratio of the focallength of the 32nd lens group G32 to the focal length of the third lensgroup G3. Successful optical performance upon correcting the image blur(vibration proofing) and size reduction of the optical system can beachieved by satisfying the conditional expression (2).

If the ratio thereof is less than a lower limit of the conditionalexpression (2), refractive power of the third lens group G3 is reduced,size reduction of the lens barrel becomes difficult. If the refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lowerlimit of the conditional expression (2) to 2.50.

If the ratio thereof is more than an upper limit of the conditionalexpression (2), refractive power of the third lens group G3 increases,correction of spherical aberration and coma aberration in the telephotoend state becomes difficult, and therefore such a case is notpreferable. Refractive power of the 32nd lens group G32 also increases,and a shift amount upon correcting the image blur (vibration proofing)increases, and size reduction of the lens barrel becomes difficult.

The effect of the first embodiment can be ensured by setting the upperlimit of the conditional expression (2) to 4.00.

The zoom optical system ZL according to the first embodiment preferablysatisfies the following conditional expression (3):0.50<|f31|/f3<2.00  (3)

where f31 denotes a focal length of the 31st lens group G31, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (3) specifies a proper ratio of the focallength of the 31st lens group 31 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(3).

If the ratio thereof is less than a lower limit of the conditionalexpression (3), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lowerlimit of the conditional expression (3) to 0.70.

If the ratio thereof is more than an upper limit of the conditionalexpression (3), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the first embodiment can be ensured by setting the upperlimit of the conditional expression (3) to 1.50.

The zoom optical system ZL according to the first embodiment preferablysatisfies the following conditional expression (4):1.00<|f33|/f3  (4)

where f33 denotes a focal length of the 33rd lens group G33, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (4) specifies a proper ratio of the focallength of the 33rd lens group G33 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(4).

If the ratio thereof is less than a lower limit of the conditionalexpression (4), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If therefractive power of the first lens group G1 and the second lens group G2is increased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lowerlimit of the conditional expression (4) to 2.00.

In the zoom optical system ZL according to the first embodiment, the32nd lens group G32 is preferably configured of a single lens.

According to this configuration, variations in decentering comaaberration and variations in curvature of field upon correcting theimage blur can be successfully suppressed. Moreover, size reduction ofthe image blur correction mechanism can also be achieved.

The zoom optical system ZL according to the first embodiment has a stopS, and the stop S preferably moves along an optical axis directionintegrally with the third lens group G3 upon zooming.

According to this configuration, lens barrel structure can be simplifiedand size reduction of the lens barrel can be achieved.

The zoom optical system ZL according to the first embodiment has a stopS, and the stop S is preferably arranged between the second lens groupG2 and an image surface I.

According to this configuration, curvature of field and astigmatism canbe successfully corrected.

The zoom optical system ZL according to the first embodiment preferablysatisfies the following conditional expression (5):30.00°<ωw<80.00°  (5)

where ωw denotes a half angle of view in a wide-angle end state.

The conditional expression (5) represents a condition specifying a valueof an angle of view in a wide-angle end state. While the zoom opticalsystem ZL has a wide angle of view, coma aberration, distortion, andcurvature of field can be successfully corrected by satisfying theconditional expression (5).

Further successful aberration correction can be made by setting thelower limit of the conditional expression (5) to 33.00°. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (5) to 36.00°.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (5) to 77.00°.

The zoom optical system ZL according to the first embodiment preferablysatisfies the following conditional expression (6):2.00<ft/fw<15.00  (6)

where ft denotes a focal length of the zoom optical system in thetelephoto end state, and

fw denotes a focal length of the zoom optical system in a wide-angle endstate.

The conditional expression (6) represents a condition specifying a ratioof the focal length of the zoom optical system in the telephoto endstate to the focal length of the zoom optical system in the wide-angleend state. In the present zoom optical system ZL, a high zoom ratio canbe obtained, and simultaneously spherical aberration and coma aberrationcan also be successfully corrected by satisfying the conditionalexpression (6).

Further successful aberration correction can be made by setting thelower limit of the conditional expression (6) to 2.30. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (6) to 2.50. An effect of the firstembodiment can be exhibited to a maximum by setting the lower limit ofthe conditional expression (6) to 2.70.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (6) to 10.00. Still furthersuccessful aberration correction can be made by setting the upper limitof the conditional expression (6) to 7.00.

The zoom optical system ZL according to the first embodiment preferablysatisfies the following conditional expression (7):3.60<f1/f3<8.00  (7)

where f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (7) specifies a proper ratio of the focallength of the first lens group G1 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(7).

If the ratio thereof is less than a lower limit of the conditionalexpression (7), refractive power of the first lens group G1 increases,correction of coma aberration, astigmatism, and curvature of field inthe telephoto end state becomes difficult, and therefore such a case isnot preferable.

The effect of the first embodiment can be ensured by setting the lowerlimit of the conditional expression (7) to 3.80.

If the ratio thereof is more than an upper limit of the conditionalexpression (7), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the first embodiment can be ensured by setting the upperlimit of the conditional expression (7) to 7.00.

The zoom optical system ZL according to the first embodiment preferablysatisfies the following conditional expression (8):0.73<(−f2)/f3<2.00  (8)

where f2 denotes a focal length of the second lens group G2, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (8) specifies a proper ratio of the focallength of the second lens group G2 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(8).

If the ratio thereof is less than a lower limit of the conditionalexpression (8), refractive power of the second lens group G2 increases,correction of coma aberration and astigmatism in a wide-angle end statebecomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lowerlimit of the conditional expression (8) to 0.75.

If the ratio thereof is more than an upper limit of the conditionalexpression (8), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the first embodiment can be ensured by setting the upperlimit of the conditional expression (8) to 1.20.

The zoom optical system ZL according to the first embodiment preferablysatisfies the following conditional expressions (9) and (10):0.14<fw/f1<0.26  (9)0.77<fw/f3<1.05  (10)

where fw denotes a focal length of the zoom optical system in awide-angle end state,

f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (9) specifies a proper ratio of the focallength of the zoom optical system in the wide-angle end state to thefocal length of the first lens group G1. Successful optical performanceand size reduction of the optical system can be achieved by satisfyingthe conditional expression (9).

If the ratio thereof is less than a lower limit of the conditionalexpression (9), refractive power of the first lens group G1 is reduced,and size reduction of the lens barrel becomes difficult. If therefractive power of the second lens of the group G2 is increased inorder to achieve size reduction, correction of coma aberration,astigmatism, and curvature of field becomes difficult, and thereforesuch a case is not preferable.

The effect of the first embodiment can be ensured by setting the lowerlimit of the conditional expression (9) to 0.15.

If the ratio thereof is more than an upper limit of the conditionalexpression (9), refractive power of the first lens group G1 increases,correction of coma aberration, astigmatism, and curvature of field inthe telephoto end state becomes difficult, and therefore such a case isnot preferable.

The effect of the first embodiment can be ensured by setting the upperlimit of the conditional expression (9) to 0.25.

The conditional expression (10) specifies a proper ratio of the focallength of the zoom optical system in the wide-angle end state to thefocal length of the third lens group G3. Successful optical performanceand size reduction of the optical system can be achieved by satisfyingthe conditional expression (10).

If the ratio thereof is less than a lower limit of the conditionalexpression (10), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lowerlimit of the conditional expression (10) to 0.80.

If the ratio thereof is more than an upper limit of the conditionalexpression (10), refractive power of the third lens group G3 increases,correction of spherical aberration, coma aberration, and astigmatismbecomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the upperlimit of the conditional expression (10) to 1.02.

The zoom optical system ZL according to the first embodiment preferablyhas, disposed in order from an object, a first lens group G1, a secondlens group G2, a third lens group G3, and a fourth lens group G4, and anair distance between the third lens group G3 and the fourth lens groupG4 is preferably varied upon zooming.

According to this configuration, while variations in sphericalaberration and curvature of field upon zooming are suppressed, asufficient zoom ratio can be ensured.

According to the first embodiment as described above, while the zoomoptical system ZL is provided with the image blur correction mechanism,the zoom optical system ZL having high optical performance can berealized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoomoptical system ZL will be described with reference to FIG. 17. As shownin FIG. 17, the camera 1 is an interchangeable lens camera (so-calledmirrorless camera) provided with the above-mentioned zoom optical systemZL as an imaging lens 2.

In the camera 1, light from an object (subject) (not shown) is collectedby the imaging lens 2 to form a subject image on an imaging surface ofan imaging unit 3 through an OLPF (optical low pass filter) (not shown).The subject image is then subjected to photoelectric conversion by aphotoelectric conversion element provided in the imaging unit 3 toproduce an image of the subject. This image is displayed on an EVF(electronic view finder) 4 provided in the camera 1. Thus, aphotographer can observe the subject through the EVF 4.

Moreover, if a release bottom (not shown) is pressed by thephotographer, the image of the subject produced in the imaging unit 3 isstored in a memory (not shown). Thus, the photographer can photographthe subject by the camera 1.

As is known also from each Example described later, while the zoomoptical system ZL is provided with the image blur correction mechanism,the zoom optical system ZL according to the first embodiment, mounted inthe camera 1 as the imaging lens 2, has high optical performance by thecharacteristic lens configuration. Thus, according to the present camera1, while the imaging device is provided with the image blur correctionmechanism, the imaging device having high optical performance can berealized.

In addition, even when the above-mentioned zoom optical system ZL ismounted on a single-lens reflex camera that has a quick return mirrorand observes the subject by a finder optical system, an effect similarto the effect of the camera 1 can be produced. Moreover, even when theabove-mentioned zoom optical system ZL is mounted on a video camera, aneffect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZLhaving the configuration will be generally described with reference toFIG. 18. First, each lens is arranged within a lens barrel in such amanner that a zoom optical system ZL is formed of a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a third lens group G3 having negative refractivepower (step S110). At this time, at least a part of the second lensgroup G2 or at least a part of the third lens group G3 is configured tobe movable, as a vibration-proof lens group for correcting the imageblur caused by camera shake or the like, so as to have a component in adirection perpendicular to the optical axis (step ST120). Each lens isarranged within a lens barrel in such a manner that at least thefollowing conditional expression (1) is satisfied among the conditionalexpressions (step ST130):4.40<f1/(−f2)<8.00  (1)

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

To take a lens arrangement according to the first embodiment as oneexample, as shown in FIG. 1, as a first lens group G1, in order from anobject, a cemented lens formed by cementing a negative meniscus lens L11and a positive meniscus lens L12 each having a convex surface facing theobject is arranged. As a second lens group G2, in order from the object,a negative meniscus lens L21 having a convex surface facing the object,a biconcave lens L22, a biconvex lens L23, and a negative meniscus lensL24 having a concave surface facing the object are arranged. As a thirdlens group G3, in order from the object, a positive meniscus lens L31having a concave surface facing the object, a cemented lens formed bycementing a biconvex lens L32 and a biconcave lens L33, a biconcave lensL34, a biconvex lens L35, a biconvex lens L36, and a negative meniscuslens L37 having a concave surface facing the object are arranged.Moreover, each lens is arranged in such a manner that the conditionalexpression (1) (a corresponding value of the conditional expression (1)is 5.33) is satisfied.

According to the method for manufacturing the zoom optical systemrelated to the first embodiment as described above, while the zoomoptical system ZL is provided with the image blur correction mechanism,the zoom optical system ZL having high optical performance can berealized.

Next, a second embodiment will be described with reference to drawings.As shown in FIG. 1, a zoom optical system ZL according to the secondembodiment has, disposed in order from an object, a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a third lens group G3 having positive refractivepower.

According to this configuration, size reduction of the lens barrel andsecurement of a sufficient zoom ratio in the wide-angle end state can beachieved.

In the zoom optical system ZL according to the second embodiment, atleast a part of the second lens group G2 or at least a part of the thirdlens group G3 is configured to be movable, as a vibration-proof lensgroup for correcting an image blur, so as to have a component in adirection perpendicular to the optical axis.

According to this configuration, size reduction of the image blurcorrection mechanism, including the vibration-proof lens group, can beachieved.

Then, under the configuration, the following conditional expression (11)is satisfied:3.60<f1/f3<8.00  (11)

where f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (11) specifies a proper ratio of the focallength of the first lens group G1 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(11).

If the ratio thereof is less than a lower limit of the conditionalexpression (11), refractive power of the first lens group G1 increases,and correction of coma aberration, astigmatism, and curvature of fieldin the telephoto end state becomes difficult, and therefore such a caseis not preferable.

An effect of the second embodiment can be ensured by setting the lowerlimit of the conditional expression (11) to 3.80.

If the ratio thereof is more than an upper limit of the conditionalexpression (11), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the second embodiment can be ensured by setting the upperlimit of the conditional expression (11) to 7.00.

In the zoom optical system ZL according to the second embodiment,zooming is preferably made by varying an air distance between the firstlens group G1 and the second lens group G2, an air distance between thesecond lens group G2 and the third lens group G3.

According to this configuration, while variations in sphericalaberration and curvature of field upon zooming are suppressed, asufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the second embodiment, thethird lens group G3 is formed of, disposed in order from an object, a31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33,and the 32nd lens group G32 is preferably configured to be movable, as avibration-proof lens group, so as to have a component in a directionperpendicular to the optical axis.

According to this configuration, successful optical performance can berealized upon correcting the image blur (vibration proofing). Moreover,size reduction of the image blur correction mechanism can also beachieved.

In the zoom optical system ZL according to the second embodiment, the32nd lens group G32 preferably has negative refractive power.

According to this configuration, successful optical performance can berealized upon correcting the image blur (vibration proofing).

The zoom optical system ZL according to the second embodiment preferablysatisfies the following conditional expression (12):2.00<(−f32)/f3<6.00  (12)

where f32 denotes a focal length of the 32nd lens group G32, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (12) specifies a proper ratio of the focallength of the 32nd lens group to the focal length of the third lensgroup G3. Successful optical performance upon correcting the image blur(vibration proofing) and size reduction of the optical system can beachieved by satisfying the conditional expression (12).

If the ratio thereof is less than a lower limit of the conditionalexpression (12), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the lowerlimit of the conditional expression (12) to 2.50.

If the ratio thereof is more than an upper limit of the conditionalexpression (12), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable. Moreover, refractive power of the 32nd lens group G32 isreduced and a shift amount upon correcting the image blur (vibrationproofing) increases, and size reduction of the lens barrel becomesdifficult, and therefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the upperlimit of the conditional expression (12) to 4.00.

The zoom optical system ZL according to the second embodiment preferablysatisfies the following conditional expression (13):0.50<|f31|/f3<2.00  (13)

where f31 denotes a focal length of the 31st lens group G31, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (13) specifies a proper ratio of the focallength of the 31st lens group G31 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(13).

If the ratio thereof is less than a lower limit of the conditionalexpression (13), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the lowerlimit of the conditional expression (13) to 0.70.

If the ratio thereof is more than an upper limit of the conditionalexpression (13), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the second embodiment can be ensured by setting the upperlimit of the conditional expression (13) to 1.50.

The zoom optical system ZL according to the second embodiment preferablysatisfies the following conditional expression (14):1.00<|f33|/f3  (14)

where f33 denotes a focal length of the 33rd lens group G33, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (14) specifies a proper ratio of the focallength of the 33rd lens group G33 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(14).

If the ratio thereof is less than a lower limit of the conditionalexpression (14), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the lowerlimit of the conditional expression (14) to 2.00.

In the zoom optical system ZL according to the second embodiment, the32nd lens group G32 is preferably configured of a single lens.

According to this configuration, variations in decentering comaaberration and variations in curvature of field upon correcting theimage blur can be successfully corrected. Moreover, size reduction ofthe image blur correction mechanism can also be achieved.

The zoom optical system ZL according to the second embodiment has a stopS, and the stop S preferably moves along an optical axis directionintegrally with the third lens group G3 upon zooming.

According to this configuration, lens barrel structure can besimplified, and size reduction of the lens barrel can be achieved.

The zoom optical system ZL according to the second embodiment has a stopS, and the stop S is preferably arranged between the second lens groupG2 and the image surface I.

According to this configuration, curvature of field and astigmatism canbe successfully corrected.

The zoom optical system ZL according to the second embodiment preferablysatisfies the following conditional expression (15):30.00°<ωw<80.00°  (15)

where ωw denotes a half angle of view in the wide-angle end state.

The conditional expression (15) represents a condition specifying avalue of an angle of view in the wide-angle end state. While the zoomoptical system ZL has a wide angle of view, coma aberration, distortion,and curvature of field can be successfully corrected by satisfying theconditional expression (15).

Further successful aberration correction can be made by setting a lowerlimit of the conditional expression (15) to 33.00°. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (15) to 36.00°.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (15) to 77.00.

The zoom optical system ZL according to the second embodiment preferablysatisfies the following conditional expression (16):2.00<ft/fw<15.00  (16)

where ft denotes a focal length of the zoom optical system in thetelephoto end state, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

The conditional expression (16) represents a condition specifying aratio of the focal length of the zoom optical system in the telephotoend state to the focal length of the zoom optical system in thewide-angle end state. In the present zoom optical system ZL, a high zoomratio can be obtained, and simultaneously spherical aberration and comaaberration can be successfully corrected by satisfying the conditionalexpression (16).

Further successful aberration correction can be made by setting a lowerlimit of the conditional expression (16) to 2.30. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (16) to 2.50. An effect of the secondembodiment can be exhibited to a maximum by setting the lower limit ofthe conditional expression (16) to 2.70.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (16) to 10.00. Still furthersuccessful aberration correction can be made by setting the upper limitof the conditional expression (16) to 7.00.

According to the second embodiment as described above, while the zoomoptical system ZL is provided with the image blur correction mechanism,the zoom optical system ZL having high optical performance can berealized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoomoptical system ZL will be described with reference to FIG. 17. Thecamera 1 is identical with the camera 1 in the first embodiment, and theconfiguration thereof has been already described, and the descriptionherein is omitted.

As is known also from each Example described later, while the zoomoptical system ZL is provided with the image blur correction mechanism,the zoom optical system ZL according to the second embodiment, mountedin the camera 1 as the imaging lens 2, has high optical performance bythe characteristic lens configuration. Thus, according to the presentcamera 1, while the imaging device is provided with the image blurcorrection mechanism, the imaging device having high optical performancecan be realized.

In addition, even when the above-mentioned zoom optical system ZL ismounted on a single-lens reflex camera that has a quick return mirrorand observes the subject by a finder optical system, an effect similarto the effect of the camera 1 can be produced. Moreover, even when theabove-mentioned zoom optical system ZL is mounted on a video camera, aneffect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZLhaving the configuration will be generally described with reference toFIG. 19. First, each lens is arranged within a lens barrel in such amanner that a zoom optical system ZL has a first lens group G1 havingpositive refractive power, a second lens group G2 having negativerefractive power, and a third lens group G3 having positive refractivepower (step ST210). At this time, at least a part of the second lensgroup G2 or at least a part of the third lens group G3 is configured tobe movable, as a vibration-proof lens group for correcting an image blur(caused by camera shake or the like), so as to have a component in adirection perpendicular to an optical axis (step ST220). Each lens isarranged within the lens barrel in such a manner that at least thefollowing conditional expression (11) among the conditional expressions(step ST230):3.60<f1/f3<8.00  (11)

where f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

To take a lens arrangement according to the second embodiment as oneexample, as shown in FIG. 1, as the first lens group G1, in order froman object, a cemented lens formed by cementing a negative meniscus lensL11 and a positive meniscus lens L12 each having a convex surface facingthe object is arranged. As the second lens group G2, in order from theobject, a negative meniscus lens L21 having a convex surface facing theobject, a biconcave lens L22, a biconvex lens L23, and a negativemeniscus lens L24 having a concave surface facing the object arearranged. As the third lens group G3, in order from the object, apositive meniscus lens L31 having a convex surface facing the object, acemented lens formed by cementing a biconvex lens L32 and a biconcavelens L33, a biconcave lens L34, a biconvex lens L35, a biconvex lensL36, and a negative meniscus lens L37 having a concave surface facingthe object are arranged. Moreover, each lens is arranged in such amanner that the conditional expression (11) (a corresponding value ofthe conditional expression (11) is 4.06) is satisfied.

According to the method for manufacturing the zoom optical systemrelated to the second embodiment as described above, while the zoomoptical system ZL is provided with the image blur correction mechanism,the zoom optical system ZL having high optical performance can berealized.

Next, a third embodiment will be described with reference to drawings.As shown in FIG. 1, a zoom optical system ZL according to the thirdembodiment is formed of, disposed in order from an object, a first lensgroup G1 having positive refractive power, a second lens group G2 havingnegative refractive power, and a third lens group G3 having positiverefractive power.

According to this configuration, size reduction of the lens barrel andsecurement of a sufficient zoom ratio in the wide-angle end state can beachieved.

The zoom optical system ZL according to the third embodiment moves thefirst lens group G1 to a direction of the object along an optical axisdirection upon zooming from the wide-angle end state to the telephotoend state.

According to this configuration, a sufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the third embodiment,focusing is made by moving at least a part of the third lens group G3along the optical axis direction.

According to this configuration, variations in aberration (for example,spherical aberration) upon focusing can be suppressed.

Then, under the configuration, the following conditional expression (17)is satisfied:0.73<(−f2)/f3<2.00  (17)

where f2 denotes a focal length of the second lens group G2, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (17) specifies a proper ratio of the focallength of the second lens group G2 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(17).

If the ratio thereof is less than a lower limit of the conditionalexpression (17), refractive power of the second lens group G2 increases,correction of coma aberration and astigmatism in the wide-angle endstate becomes difficult, and therefore such a case is not preferable.

An effect of the third embodiment can be ensured by setting the lowerlimit of the conditional expression (17) to 0.75.

If the ratio thereof is more than an upper limit of the conditionalexpression (17), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the third embodiment can be ensured by setting the upperlimit of the conditional expression (17) to 1.20.

In the zoom optical system ZL according to the third embodiment, zoomingis preferably made by varying an air distance between the first lensgroup G1 and the second lens group G2 and an air distance between thesecond lens group G2 and the third lens group G3.

According to this configuration, while variations in sphericalaberration and curvature of field upon zooming are suppressed, asufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the third embodiment, thethird lens group G3 is formed of, disposed in order from the object, a3A lens group G3A and a 3B lens group G3B each having positiverefractive power, in which focusing is preferably made by moving the 3Alens group G3A along the optical axis direction.

According to this configuration, variations in aberration (for example,spherical aberration) upon focusing can be suppressed.

The zoom optical system ZL according to the third embodiment preferablysatisfies the following conditional expression (18):1.00<f3A/f3<4.00  (18)

where f3A denotes a focal length of the 3A lens group G3A.

The conditional expression (18) specifies a proper ratio of the focallength of the 3A lens group G3A to the focal length of the third lensgroup G3. Successful optical performance upon focusing and sizereduction of the optical system can be achieved by satisfying theconditional expression (18).

If the ratio thereof is less than a lower limit of the conditionalexpression (18), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the lowerlimit of the conditional expression (18) to 1.50.

If the ratio thereof is more than an upper limit of the conditionalexpression (18), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the third embodiment can be ensured by setting the upperlimit of the conditional expression (18) to 3.50.

In the zoom optical system ZL according to the third embodiment, the 3Alens group G3A is preferably formed of a single lens.

According to this configuration, size reduction of a focusing mechanismcan be achieved.

The zoom optical system ZL according to the third embodiment preferablysatisfies the following conditional expression (19):1.00<|f3B|/f3<5.00  (19)

where f3 denotes a focal length of the third lens group G3.

The conditional expression (19) specifies a proper ratio of the focallength of the 3B lens group to the focal length of the third lens groupG3. Successful optical performance and size reduction of the opticalsystem can be achieved by satisfying the conditional expression (19).

If the ratio thereof is less than a lower limit of the conditionalexpression (19), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the lowerlimit of the conditional expression (19) to 1.20.

If the ratio thereof is more than an upper limit of the conditionalexpression (19), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the third embodiment can be ensured by setting the upperlimit of the conditional expression (19) to 3.00.

In the zoom optical system ZL according to the third embodiment, atleast a part of the 3B lens group G3B is preferably configured to bemovable, as a vibration-proof lens group VR for correcting an imageblur, so as to have a component in a direction perpendicular to theoptical axis.

According to this configuration, successful optical performance uponcorrecting the image blur (vibration proofing) can be realized.Moreover, size reduction of an image blur correction mechanism,including the vibration-proof lens group VR, can be achieved.

In the zoom optical system ZL according to the third embodiment, thevibration-proof lens group VR preferably has negative refractive power.

According to this configuration, successful optical performance uponcorrecting the image blur (vibration proofing) can be realized.

The zoom optical system ZL according to the third embodiment preferablysatisfies the following conditional expression (20):2.00<|fvr|/f3<6.00  (20)

where fvr denotes a focal length of the vibration-proof lens group VR.

The conditional expression (20) specifies a proper ratio of the focallength of the vibration-proof lens group VR to the focal length of thethird lens group G3. Successful optical performance upon correcting theimage blur and size reduction of the optical system can be achieved bysatisfying the conditional expression (20).

If the ratio thereof is less than a lower limit of the conditionalexpression (20), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the lowerlimit of the conditional expression (20) to 2.50.

If the ratio thereof is more than an upper limit of the conditionalexpression (20), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable. Moreover, refractive power of the vibration-proof lens groupVR is reduced, and a shift amount upon correcting the image blur(vibration proofing) increases, and size reduction of the lens barrelbecomes difficult.

The effect of the third embodiment can be ensured by setting the upperlimit of the conditional expression (20) to 4.00.

In the zoom optical system ZL according to the third embodiment, thevibration-proof lens group VR is preferably formed of a single lens.

According to this configuration, size reduction of the image blurcorrection mechanism can be achieved.

The zoom optical system ZL according to the third embodiment has a stopS, and the stop S preferably moves along the optical axis directionintegrally with the third lens group G3 upon zooming.

According to this configuration, lens barrel structure can besimplified, and size reduction of the lens barrel can be achieved.

The zoom optical system ZL according to the third embodiment has a stopS, and the stop S is preferably arranged between the second lens groupG2 and the image surface I.

According to this configuration, curvature of field and astigmatism canbe successfully corrected.

The zoom optical system ZL according to the third embodiment preferablysatisfies the following conditional expression (21):30.00°<ωw<80.00°  (21)

where ωw denotes a half angle of view in the wide-angle end state.

The conditional expression (21) represents a condition specifying avalue of an angle of view in the wide-angle end state. While the zoomoptical system ZL has a wide angle of view, coma aberration, distortion,and curvature of field can be successfully corrected by satisfying theconditional expression (21).

Further successful aberration correction can be made by setting a lowerlimit of the conditional expression (21) to 33.00°. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (21) to 36.00°.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (21) to 77.00°.

The zoom optical system ZL according to the third embodiment preferablysatisfies the following conditional expression (22):2.00<ft/fw<15.00  (22)

where ft denotes a focal length of the zoom optical system in thetelephoto end state, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

The conditional expression (22) represents a condition specifying aratio of the focal length of the zoom optical system in the telephotoend state to the focal length of the zoom optical system in thewide-angle end state. In the present zoom optical system ZL, a high zoomratio can be obtained, and simultaneously spherical aberration and comaaberration can be successfully corrected by satisfying the conditionalexpression (22).

Further successful aberration correction can be made by setting thelower limit of the conditional expression (22) to 2.30. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (22) to 2.50. The effect of the thirdembodiment can be exhibited to a maximum by setting the lower limit ofthe conditional expression (22) to 2.70.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (22) to 10.00. Still furthersuccessful aberration correction can be made by setting the upper limitof the conditional expression (22) to 7.00.

According to the third embodiment as described above, the zoom opticalsystem ZL having high optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoomoptical system ZL will be described with reference to FIG. 17. Thecamera 1 is identical with the camera 1 in the first embodiment, and theconfiguration has been already described, and therefore the descriptionherein is omitted.

As is known also from each Example described later, the zoom opticalsystem ZL according to the third embodiment, mounted in the camera 1 asan imaging lens 2, has high optical performance by the characteristiclens configuration. Thus, according to the present camera 1, the imagingdevice having high optical performance can be realized.

In addition, even when the above-mentioned zoom optical system ZL ismounted on a single-lens reflex camera that has a quick return mirrorand observes the subject by a finder optical system, an effect similarto the effect of the camera 1 can be produced. Moreover, even when theabove-mentioned zoom optical system ZL is mounted on a video camera, aneffect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZLhaving the configuration will be generally described with reference toFIG. 20. First, each lens is arranged within a lens barrel in such amanner that a zoom optical system ZL is formed of a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a third lens group G3 having positive refractivepower (step ST310). At this time, each lens is arranged in such a mannerthat the first lens group G1 moves to a direction of an object along anoptical axis direction upon zooming from a wide-angle end state to atelephoto end state (step ST320). Each lens is arranged in such a mannerthat focusing is made by moving at least a part of the third lens groupG3 along the optical axis direction (step ST330). Moreover, each lens isarranged within the lens barrel in such a manner that at least thefollowing conditional expression (17) is satisfied among the conditionalexpressions (step ST340):0.73<(−f2)/f3<2.00  (17)

where f2 denotes a focal length of the second lens group G2, and

f3 denotes a focal length of the third lens group G3.

To take a lens arrangement according to the third embodiment as oneexample, as shown in FIG. 1, in order from an object, a cemented lensformed by cementing a negative meniscus lens L11 and a positive meniscuslens L12 each having a convex surface facing the object is arranged. Asthe second lens group G2, in order from the object, a negative meniscuslens L21 having a convex surface facing the object, a biconcave lensL22, a biconvex lens L23, and a negative meniscus lens L24 having aconcave surface facing the object are arranged. As the third lens groupG3, in order from the object, a positive meniscus lens L31 having aconcave surface facing the object, a cemented lens formed by cementing abiconvex lens L32 and a biconcave lens L33, a biconcave lens L34, abiconvex L35, a biconvex lens L36, and a negative meniscus lens L37having a concave surface facing the object are arranged. Moreover, eachlens is arranged in such a manner that the conditional expression (17)(a corresponding value of the conditional expression (17) is 0.76) issatisfied.

According to the method for manufacturing the zoom optical systemrelated to the third embodiment as described above, the zoom opticalsystem ZL having has high optical performance can be realized.

Next, a fourth embodiment will be described with reference to drawings.As shown in FIG. 1, a zoom optical system ZL according to the fourthembodiment has, disposed in order from an object, a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a third lens group G3 having positive refractivepower.

According to this configuration, size reduction of a lens barrel in thewide-angle end state can be achieved.

The zoom optical system ZL according to the fourth embodiment moves thefirst lens group G1 to a direction of the object along an optical axisdirection upon zooming from a wide-angle end state to a telephoto endstate.

According to this configuration, a sufficient zoom ratio can be ensured.

Then, under the configuration, the following conditional expressions(23) and (24) are satisfied:0.14<fw/f1<0.26  (23)0.77<fw/f3<1.05  (24)

where fw denotes a focal length of the zoom optical system in thewide-angle end state,

f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (23) specifies a proper ratio of the focallength of the zoom optical system in a wide-angle end state to the focallength of the first lens group G1. Successful optical performance andsize reduction of the optical system can be achieved by satisfying theconditional expression (23).

If the ratio thereof is less than a lower limit of the conditionalexpression (23), refractive power of the first lens group G1 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the second lens group G2 is increased in order to achieve sizereduction, correction of coma aberration, astigmatism, and curvature offield becomes difficult, and therefore such a case is not preferable.

An effect of the fourth embodiment can be ensured by setting the lowerlimit of the conditional expression (23) to 0.15.

If the ratio thereof is more than an upper limit of the conditionalexpression (23), refractive power of the first lens group G1 increases,correction of coma aberration, astigmatism, and curvature of field inthe telephoto end state becomes difficult, and therefore such a case isnot preferable.

The effect of the fourth embodiment can be ensured by setting the upperlimit of the conditional expression (23) to 0.25.

The conditional expression (24) specifies a proper ratio of the focallength of the zoom optical system in a wide-angle end state to the focallength of the third lens group G3. Successful optical performance andsize reduction of the optical system can be achieved by satisfying theconditional expression (24).

If the ratio thereof is less than a lower limit of the conditionalexpression (24), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the lowerlimit of the conditional expression (24) to 0.80.

If the ratio thereof is more than an upper limit of the conditionalexpression (24), refractive power of the third lens group G3 increases,and correction of spherical aberration, coma aberration, and astigmatismbecomes difficult, and therefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the upperlimit of the conditional expression (24) to 1.02.

In the zoom optical system ZL according to the fourth embodiment,zooming is preferably made by varying an air distance between the firstlens group G1 and the second lens group G2, an air distance between thesecond lens group G2 and the third lens group G3.

According to this configuration, while variations in sphericalaberration and curvature of field upon zooming are suppressed, asufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the fourth embodiment, atleast a part of the second lens group G2 or at least a part of the thirdlens group G3 is preferably configured to be movable, as avibration-proof lens group for correcting an image blur (caused bycamera shake or the like), so as to have a component in a directionperpendicular to the optical axis.

According to this configuration, size reduction of an image blurcorrection mechanism, including the vibration-proof lens group, can beachieved.

In the zoom optical system ZL according to the fourth embodiment,focusing is preferably made by moving at least a part of the third lensgroup G3 along the optical axis direction.

According to this configuration, variations in aberration (for example,spherical aberration) upon focusing can be suppressed.

In the zoom optical system ZL according to the fourth embodiment, thethird lens group G3 is formed of, disposed in order from the object, a31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33,and the 32nd lens group G32 is preferably configured to be movable, as avibration-proof lens group, so as to have a component in a directionperpendicular to the optical axis.

According to this configuration, successful optical performance uponcorrecting the image blur (vibration proofing) can be realized.Moreover, size reduction of the image blur correction mechanism can beachieved.

In the zoom optical system ZL according to the fourth embodiment, the32nd lens group G32 preferably has negative refractive power.

According to this configuration, successful optical performance uponcorrecting the image blur (vibration proofing) can be realized.

The zoom optical system ZL according to the fourth embodiment preferablysatisfies the following conditional expression (25):2.00<(−f32)/f3<6.00  (25)

where f32 denotes a focal length of the 32nd lens group G32, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (25) specifies a proper ratio of the focallength of the 32nd lens group G32 to the focal length of the third lensgroup G3. Successful optical performance upon correcting the image blur(vibration proofing) and size reduction of the optical system can beachieved by satisfying the conditional expression (25).

If the ratio thereof is less than a lower limit of the conditionalexpression (25), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the lowerlimit of the conditional expression (25) to 2.50.

If the ratio thereof is more than an upper limit of the conditionalexpression (25), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult. Moreover, refractive power of the32nd lens group G32 is reduced and a shift amount upon correcting theimage blur (vibration proofing) increases, and size reduction of thelens barrel becomes difficult.

The effect of the fourth embodiment can be ensured by setting the upperlimit of the conditional expression (25) to 4.00.

The zoom optical system ZL according to the fourth embodiment preferablysatisfies the following conditional expression (26):0.50<|f31|/f3<2.00  (26)

where f31 denotes a focal length of the 31st lens group G31, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (26) specifies a proper ratio of the focallength of the 31st lens group G31 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(26).

If the ratio thereof is less than a lower limit of the conditionalexpression (26), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the lowerlimit of the conditional expression (26) to 0.70.

If the ratio thereof is more than an upper limit of the conditionalexpression (26), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult, and therefore such a case is notpreferable.

The effect of the fourth embodiment can be ensured by setting the upperlimit of the conditional expression (26) to 1.50.

The zoom optical system ZL according to the fourth embodiment preferablysatisfies the following conditional expression (27):1.00<|f33|/f3  (27)

where f33 denotes a focal length of the 33rd lens group G33, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (27) specifies a proper ratio of the focallength of the 33rd lens group G33 to the focal length of the third lensgroup G3. Successful optical performance and size reduction of theoptical system can be achieved by satisfying the conditional expression(27).

If the ratio thereof is less than a lower limit of the conditionalexpression (27), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. If refractivepower of the first lens group G1 and the second lens group G2 isincreased in order to achieve size reduction, correction of comaaberration, astigmatism, and curvature of field becomes difficult, andtherefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the lowerlimit of the conditional expression (27) to 2.00.

In the zoom optical system ZL according to the fourth embodiment, the32nd lens group G32 is preferably configured of a single lens.

According to this configuration, variations in decentering comaaberration and variations in curvature of field upon correcting theimage blur can be successfully corrected. Moreover, size reduction ofthe image blur correction mechanism can be achieved.

In the zoom optical system 1ZL according to the fourth embodiment, the31st lens group G31 is preferably formed of, disposed in order from theobject, a front group G3F having positive refractive power and a reargroup G3R, in which focusing is preferably made by moving the frontgroup G3F along the optical axis direction.

According to this configuration, variations in aberration (for example,spherical aberration) upon focusing can be suppressed.

The zoom optical system ZL according to the fourth embodiment has a stopS, and the stop S preferably moves along the optical axis directionintegrally with the third lens group G3 upon zooming.

According to this configuration, lens barrel structure can besimplified, and size reduction of the lens barrel can be achieved.

The zoom optical system ZL according to the fourth embodiment has a stopS, and the stop S is preferably arranged between the second lens groupG2 and the image surface I.

According to this configuration, curvature of field and astigmatism canbe successfully corrected.

The zoom optical system ZL according to the fourth embodiment preferablysatisfies the following conditional expression (28):30.00°<ωw<80.00°  (28)

where ωw denotes a half angle of view in a wide-angle end state.

The conditional expression (28) represents a condition specifying avalue of an angle of view in the wide-angle end state. While the zoomoptical system ZL has a wide angle of view, coma aberration, distortion,and curvature of field can be successfully corrected by satisfying theconditional expression (28).

Further successful aberration correction can be made by setting a lowerlimit of the conditional expression (28) to 33.00°. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (28) to 36.00°.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (28) to 77.00°.

The zoom optical system ZL according to the fourth embodiment preferablysatisfies the following conditional expression (29):2.00<ft/fw<15.00  (29)

where ft denotes a focal length of the zoom optical system in thetelephoto end state, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

The conditional expression (29) represents a condition specifying aratio of the focal length of the zoom optical system in the telephotoend state to the focal length of the zoom optical system in thewide-angle end state. In the present zoom optical system ZL, a high zoomratio can be obtained, and simultaneously spherical aberration and comaaberration can be successfully corrected by satisfying the conditionalexpression (29).

Further successful aberration correction can be made by setting a lowerlimit of the conditional expression (29) to 2.30. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (29) to 2.50. The effect of the fourthembodiment can be exhibited to a maximum by setting the lower limit ofthe conditional expression (29) to 2.70.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (29) to 10.00. Still furthersuccessful aberration correction can be made by setting the upper limitof the conditional expression (29) to 7.00.

According to the fourth embodiment as described above, the zoom opticalsystem ZL having high optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoomoptical system ZL will be described with reference to FIG. 17. Thecamera 1 is identical with the camera 1 in the first embodiment, and theconfiguration has been already described above, and therefore thedescription herein is omitted.

As is known also from each Example described later, the zoom opticalsystem ZL according to the fourth embodiment, mounted in the camera 1 asan imaging lens 2, has high optical performance by the characteristiclens configuration. Thus, according to the present camera 1, the imagingdevice having high optical performance can be realized.

In addition, even when the above-mentioned zoom optical system ZL ismounted on a single-lens reflex camera that has a quick return mirrorand observes the subject by a finder optical system, an effect similarto the effect of the camera 1 can be produced. Moreover, even when theabove-mentioned zoom optical system ZL is mounted on a video camera, aneffect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZLhaving the configuration will be generally described with reference toFIG. 21. First, each lens is arranged within a lens barrel in such amanner that the zoom optical system ZL has a first lens group G1 havingpositive refractive power, a second lens group G2 having negativerefractive power, and a third lens group G3 having positive refractivepower (step ST410). At this time, each lens is arranged in such a mannerthat the first lens group G1 moves to a direction of an object along anoptical axis direction upon zooming from a wide-angle end state to atelephoto end state (step ST420). Each lens is arranged within the lensbarrel in such a manner that at least the following conditionalexpressions (23) and (24) are satisfied among the conditionalexpressions (step ST430):0.14<fw/f1<0.26  (23)0.77<fw/f3<1.05  (24)

where fw denotes a focal length of the zoom optical system in thewide-angle end state,

f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

To take a lens arrangement according to the fourth embodiment as oneexample, as shown in FIG. 1, as a first lens group G1, in order from anobject, a cemented lens formed by cementing a negative meniscus lens L11and a positive meniscus lens L12 each having a convex surface facing theobject is arranged. As a second lens group G2, in order from the object,a negative meniscus lens L21 having a convex surface facing the object,a biconcave lens L22, a biconvex lens L23, and a negative meniscus lensL24 having a concave surface facing the object are arranged. As a thirdlens group G3, in order from the object, a positive meniscus lens L31having a concave surface facing the object, a cemented lens formed bycementing a biconvex lens L32 and a biconcave lens L33, a biconcave lensL34, a biconvex L35, a biconvex lens L36, and a negative meniscus lensL37 having a concave surface facing the object are arranged. Moreover,each lens is arranged in such a manner that conditional expressions (23)and (24) (a corresponding value of the conditional expression (23) is0.22 and a corresponding value of the conditional expression (24) is 0.90) are satisfied.

According to the method for manufacturing the zoom optical systemaccording to the fourth embodiment as described above, the zoom opticalsystem ZL having high optical performance can be obtained.

Examples According to First to Fourth Embodiments

Next, each Example according to each of the first to fourth embodimentswill be described based on drawings. Tables 1 to 4 are provided below,and these Tables indicate specifications in Examples 1 to 4,respectively.

However, Example 4 corresponds to only the second and fourthembodiments.

FIGS. 1, 5, 9, and 13 each are a cross-sectional drawing showing aconfiguration of each of zoom optical systems ZL (ZL1 to ZL4) accordingto Examples 1, 2, 3, and 4. In these cross-sectional views showing thezoom optical systems ZL1 to ZL4, a moving track of each of lens groupsalong an optical axis upon zooming from a wide-angle end state (W) to atelephoto end state (T) is shown by an arrow.

Each reference sign for FIG. 1 according to Example 1 is independentlyused for each Example in order to avoid complication of the descriptionby an increase in digit number of the reference sign. Therefore, even ifreference signs common to reference signs in drawings according to otherExamples are placed, the reference signs do not necessarily provideconfigurations common to the configurations in other Examples.

In each Example, a d-line (wavelength: 587.5620 nm) and a g-line(wavelength: 435.8350 nm) are selected as an object for calculation ofaberration characteristics.

In “Lens Data” in the Table, a surface number indicates an order ofoptical surfaces from an object along a direction in which a ray oflight progresses, r denotes a radius of curvature of each opticalsurface, D denotes a distance to the next lens surface being thedistance on an optical axis from each optical surface to the nextoptical surface (or image surface), υd denotes the Abbe number of amaterial of an optical member on the basis of the d-line, and nd denotesa refractive index for the d-line of the material of the optical member.Moreover, (Variable) indicates a variable distance to the next lenssurface, “∞” in a radius of curvature indicates a flat surface or anaperture, and (Stop S) indicates an aperture stop S. A refractive index(d-line) of air “1.000000” is omitted. When the optical surface isaspherical, “*” is placed on a left side of the surface number, and aparaxial radius of curvature is shown in a column of the radius ofcurvature r.

In “Aspherical Surface Data” in the Table, a shape of an asphericalsurface shown in “Lens Data” is expressed by the following expression(a). Here, y denotes a height in a direction perpendicular to an opticalaxis, X(y) denotes an amount of displacement (amount of sag) in anoptical axis direction at a height y, r denotes a radius of curvature(paraxial radius of curvature) of a reference spherical surface, κdenotes a conical coefficient, and An represents an n-th asphericalcoefficient. In addition, “E-n” represents “×10^(−n),” and for example,“1.234E-05” represents “1.234×10⁻⁵.”X(y)=(y ² /r)/[1+{1−κ(y ² /r ²)}^(1/2)]+A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y¹⁰  (a)

In “Various Data” in the Table, f denotes a focal length of a whole lenssystem, Fno denotes an F-number, ω denotes a half angle of view (a unit:°), Y denotes an image height, TL denotes a total length of a lenssystem (a distance from a lens forefront surface to an image surface Ion an optical axis), and Bf denotes a back focus (a distance from a lensfinal surface to the image surface I on the optical axis).

In “Variable Distance Data” in the Table, a focal length f or imagingmagnification β of a zoom optical system in a wide-angle end state, anintermediate focal length state, and a telephoto end state upon focusingon infinity and a short distant object (an imaging distance R=1.0 m),and a value of each variable distance is shown. In addition, D0 denotesa distance from an object surface to a first surface, and Di (where, iis an integer) denotes a variable distance between an i-th surface and a(i+1)-th surface.

In “Lens Group Data” in the Table, a start surface number (surfacenumber on a side closest to an object) of each group is shown in a groupfirst surface, and a focal length of each group is shown in a groupfocal length.

In “Conditional Expression Corresponding Value” in the Table, valuescorresponding to the conditional expressions (1) to (29) are shown.

In the following, in all the values of the specifications, unlessotherwise stated, “mm” is generally used for the focal length f, theradius of curvature r, the distance to the next lens surface D and otherlengths, and the like entered therein. However, equivalent opticalperformance can be obtained even if the optical system is proportionallyscaled up or scaled down, and therefore the values are not limitedthereto. Moreover, the unit is not limited to “mm,” and otherappropriate units can be used.

The description with regard to Table so far is common in all Examples,and the description in the following is omitted.

(Example 1)

Example 1 will be described using FIG. 1, FIGS. 2A-2C, 3A-3C, 4A-4C andTable 1. As shown in FIG. 1, a zoom optical system ZL (ZL1) according toExample 1 is configured of, disposed in order from an object along anoptical axis, a first lens group G1 having positive refractive power, asecond lens group G2 having negative refractive power, and a third lensgroup G3 having positive refractive power.

The first lens group G1 is configured of, disposed in order from theobject, a cemented lens formed by cementing a negative meniscus lens L11and a positive meniscus lens L12 each having a convex surface facing theobject.

The second lens group G2 is configured of, disposed in order from theobject, a negative meniscus lens L21 having a convex surface facing theobject, a biconcave lens L22, a biconvex lens L23, and a negativemeniscus lens L24 having a concave surface facing the object.

The third lens group G3 is configured of, disposed in order from theobject, a 31st lens group G31, a 32nd lens group G32, and a 33rd lensgroup G33.

The 31st lens group G31 is configured of, disposed in order from theobject, a front group G3F having positive refractive power, and a reargroup G3R. The front group G3F (focusing group) is configured of apositive meniscus lens L31 having a concave surface facing the object.The rear group G3R is configured of, disposed in order from the object,a cemented lens formed by cementing a biconvex lens L32 and a biconcavelens L33.

The 32nd lens group G32 (vibration-proof lens group) is configured of abiconcave lens L34. The 33rd lens group G33 is configured of, disposedin order from the object, a biconvex lens L35, a biconvex lens L36, anda negative meniscus lens L37 having a concave surface facing the object.

An aperture stop S determining an F-number is provided within the thirdlens group G3.

An image surface I is formed on an imaging element (not shown), and theimaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL1 according to Example 1, zooming from awide-angle end state to a Telephoto end state is made by varying an airdistance between the first lens group G1 and the second lens group G2and an air distance between the second lens group G2 and the third lensgroup G3. At this time, relative to the image surface I, the first lensgroup G1 monotonously moves to the object. The second lens group G2moves along the optical axis so as to draw a convex track to an image.The third lens group G3 monotonously moves to the object. The aperturestop S monotonously moves to the object integrally with the third lensgroup G3 upon zooming.

More specifically, in the zoom optical system ZL1 according to Example1, zooming from the wide-angle end state to the telephoto end state ismade by moving each of the lens groups G1 to G3 along the optical axisin such a manner that the distance between the first lens group G1 andthe second lens group G2 is enlarged, and the air distance between thesecond lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL1 according to Example 1 has a configurationin which focusing is made by moving the front group G3F of the thirdlens group G3, namely the positive meniscus lens L31 having the concavesurface facing the object, along the optical axis direction, and asshown by an arrow in FIG. 1, upon causing a change from a state offocusing on infinity to a state of focusing on the short distant object,the positive meniscus lens L31 moves from the object to the image.

Upon occurrence of an image blur, correction of the image blur(vibration proofing) on the image surface I is made by moving, as avibration-proof lens group, the 32nd lens group G32, namely thebiconcave lens L34 so as to have a component in a directionperpendicular to the optical axis.

Table 1 below shows values of each of specifications in Example 1.Surface numbers 1 to 25 in Table 1 correspond to optical surfaces m1 tom25 shown in FIG. 1, respectively.

TABLE 1 [Lens Data] Surface Number r D νd nd 1 41.994 1.800 23.801.846660 2 31.917 6.967 67.90 1.593190 3 1604.312  D3 (Variable) 479.168 1.500 32.35 1.850260 5 11.927 5.219 6 −52.994 1.000 42.731.834810 7 32.701 0.418 8 22.013 4.124 23.80 1.846660 9 −31.216 0.747 10−21.084 1.000 42.73 1.834810 11 −79.290 D11 (Variable) 12 −459.370 1.60749.62 1.772500 13 −32.039 D13 (Variable) 14 ∞ 2.000 (Stop S) 15 11.8866.181 82.57 1.497820 16 −23.884 0.800 23.80 1.846660 17 297.976 2.028 18−1480.750 0.800 49.62 1.772500 19 47.464 1.000 20 76.691 6.975 38.031.603420 21 −38.339 0.200 22 83.747 2.496 50.27 1.719990 23 −62.7632.711 24 −9.776 1.000 42.73 1.834810 25 −16.921 Bf [Various Data] f18.500 35.000 53.500 Fno 3.747 4.644 5.669 ω 39.556 21.350 14.391 Y14.250 14.250 14.250 TL 88.166 99.495 109.353 Bf 17.445 26.392 35.677[Variable Distance Data] (Infinity) (Imaging Distance 1 m) Wide-AngleTelephoto Wide-Angle Telephoto End Intermediate End End Intermediate Endf, β 18.500 35.000 53.500 −0.0196 −0.0365 −0.0554 D0 0.000 0.000 0.000911.8 900.5 890.6 D1 1.086 12.752 18.159 1.086 12.752 18.159  D11 15.1295.845 1.011 15.637 6.644 2.065  D13 3.924 3.924 3.924 3.416 3.125 2.871[Lens Group Data] Group Group First Group Focal Number Surface Length G11 83.101 G2 4 −15.594 G3 12 20.444 [Conditional Expression CorrespondingValue] Conditional Expression (1): f1/(−f2) = 5.33 ConditionalExpression (2): (f32)/f3 = 2.91 Conditional Expression (3): |f31|/f3 =1.02 Conditional Expression (4): |f33|/f3 = 3.59 Conditional Expression(5): ωw = 39.556 Conditional Expression (6): ft/fw = 2.89 ConditionalExpression (7): f1/f3 = 4.06 Conditional Expression (8): (−f2)/f3 = 0.76Conditional Expression (9): fw/f1 = 0.22 Conditional Expression (10):fw/f3 = 0.90 Conditional Expression (11): f1/f3 = 4.06 ConditionalExpression (12): (f32)/f3 = 2.91 Conditional Expression (13): |f31|/f3 =1.02 Conditional Expression (14): |f33|/f3 = 3.59 Conditional Expression(15): ωw = 39.556 Conditional Expression (16): ft/fw = 2.89 ConditionalExpression (17): (f2)/f3 = 0.76 Conditional Expression (18): f3A/f3 =2.18 Conditional Expression (19): |f3B|/f3 = 1.88 Conditional Expression(20): |fvr|/f3 = 2.91 Conditional Expression (21): ωw = 39.556Conditional Expression (22): ft/fw = 2.89 Conditional Expression (23):fw/f1 = 0.22 Conditional Expression (24): fw/f3 = 0.90 ConditionalExpression (25): (−f32)/f3 = 2.91 Conditional Expression (26): |f31|/f3= 1.02 Conditional Expression (27): |f33|/f3 = 3.59 ConditionalExpression (28): ωw = 39.556 Conditional Expression (29): ft/fw = 2.89

Table 1 shows that the zoom optical system ZL1 according to Example 1satisfies the conditional expressions (1) to (29).

FIGS. 2A, 2B and 2C are graphs showing aberrations of the zoom opticalsystem ZL1 according to Example 1 in a wide-angle end state (f=18.500),in which FIG. 2A is graphs showing various aberrations upon focusing oninfinity, FIG. 2B is graphs showing various aberrations (imagingmagnification β=−0.0196) upon focusing on a short distant object, andFIG. 2C is graphs showing coma aberration when an image blur iscorrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS.3A, 3B and 3C are graphs showing aberrations of the zoom optical systemZL1 according to Example 1 in an intermediate focal length state(f=35.000), in which FIG. 3A is graphs showing various aberrations uponfocusing on infinity, FIG. 3B is graphs showing various aberrations(imaging magnification β=−0.0365) upon focusing on a short distantobject, and FIG. 3C is graphs showing coma aberration when an image bluris corrected (a correction angle θ=0.30°) upon focusing on infinity.FIGS. 4A, 4B and 4C are graphs showing aberrations of the zoom opticalsystem ZL1 according to Example 1 in a telephoto end state (f=53.500),in which FIG. 4A is graphs showing various aberrations upon focusing oninfinity, FIG. 4B is graphs showing various aberrations (imagingmagnification β=−0.0554) upon focusing on a short distant object, andFIG. 4C is graphs showing coma aberration when an image blur iscorrected (a correction angle θ=0.30°) upon focusing on infinity. In thepresent Example, as shown in FIG. 2C, FIG. 3C and FIG. 4C, opticalperformance upon vibration proofing is shown in graphs showing comaaberration, centering on an image height y=0.0, corresponding to imageheights of vertically plus 10.0 and minus 10.0.

In each graph showing aberration, FNO denotes an F-number, NA denotesthe number of apertures of a ray of light incident to the first lensgroup G1, A denotes an angle, namely a half angle (unit: °) of view ofan entered ray of light, H0 denotes an object height (unit: mm), Ydenotes an image height, d denotes aberration in a d-line, and g denotesaberration in a g-line. A column without description of d or gaberration in the d-line. In the graphs showing spherical aberration, asolid line indicates spherical aberration and a broken line indicatessine conditions. In the graphs showing astigmatism, a solid lineindicates a sagittal image surface and a broken line indicates ameridional image surface. In the graph showing coma aberration, a solidline indicates meridional coma. The description of the graphs showingaberration as described above is regarded to be the same also in otherExamples, and the description thereof is omitted.

From each of the graphs showing aberration shown in FIGS. 2A-2C, 3A-3Cand 4A-4C, the zoom optical system ZL1 according to Example 1 is foundto have high imaging performance in which various aberrations aresuccessfully corrected from the wide-angle end state to the telephotoend. Moreover, the zoom optical system ZL1 is found to have high imagingperformance also upon correcting the image blur.

(Example 2)

Example 2 will be described using FIG. 5, FIGS. 6A-6C, 7A-7C, 8A-8C andTable 2. As shown in FIG. 5, a zoom optical system ZL (ZL2) according toExample 2 is configured of, disposed in order from an object along anoptical axis, a first lens group G1 having positive refractive power, asecond lens group G2 having negative refractive power, and a third lensgroup G3 having positive refractive power.

The first lens group G1 is configured of, disposed in order from theobject, a cemented lens formed by cementing a negative meniscus lens L11and a positive meniscus lens L12 each having a convex surface facing theobject.

The second lens group G2 is configured of, disposed in order from theobject, a negative meniscus lens L21 having a convex surface facing theobject, a biconcave lens L22, a biconvex lens L23, and a negativemeniscus lens L24 having a concave surface facing the object.

The third lens group G3 is configured of, disposed in order from theobject, a 31st lens group G31, a 32nd lens group G32, and a 33rd lensgroup G33.

The 31st lens group G31 is configured of, disposed in order from theobject, a front group G3F having positive refractive power and a reargroup G3R. The front group G3F (focusing group) is configured of apositive meniscus lens L31 having a concave surface facing the object.The rear group G3R is configured of, disposed in order from the object,a biconvex lens L32, and a negative meniscus lens L33 having a concavesurface facing the object.

The 32nd lens group G32 (vibration-proof lens group) is configured of anegative meniscus lens L34 having a concave surface facing the object.The 33rd lens group G33 is configured of, disposed in order from theobject, a biconvex lens L35, and a negative meniscus lens L36 having aconcave surface facing the object.

An aperture stop S determining an F-number is provided within the thirdlens group G3.

An image surface I is formed on an imaging element (not shown), and theimaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL2 according to Example 2, zooming from awide-angle end state to a telephoto end state is made by varying an airdistance between the first lens group G1 and the second lens group G2and an air distance between the second lens group G2 and the third lensgroup G3. At this time, relative to the image surface I, the first lensgroup G1 monotonously moves to the object. The second lens group G2monotonously moves to the object. The third lens group G3 monotonouslymoves to the object. The aperture stop S monotonously moves to theobject integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL2 according to Example2, zooming from the wide-angle end state to the telephoto end state ismade by moving each of the lens groups G1 to G3 along the optical axisin such a manner that the air distance between the first lens group G1and the second lens group G2 is enlarged, and the air distance betweenthe second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL2 according to Example 2 has a configurationin which focusing is made by moving the front group G3F of the thirdlens group G3, namely the positive meniscus lens L31 having the concavesurface facing the object along the optical axis direction, and as shownby an arrow in FIG. 5, upon causing a change from a state of focusing oninfinity to a state of focusing on a short distant object, the positivemeniscus lens L31 moves from the object to an image.

Upon occurrence of an image blur, correction of the image blur(vibration proofing) on the image surface I is made by moving, as avibration-proof lens group, the 32nd lens group G32, namely the negativemeniscus lens L34 having the convex surface facing the object so as tohave a component in a direction perpendicular to the optical axis.

Table 2 below shows values of each of specifications in Example 2.Surface numbers 1 to 23 in Table 2 correspond to optical surfaces m1 tom23 shown in FIG. 5, respectively.

TABLE 2 [Lens Data] Surface Number r D νd nd 1 45.608 1.800 23.801.846660 2 33.721 6.519 67.90 1.593190 3 45648.551  D3 (Variable) 445.310 1.500 32.35 1.850260 5 11.154 5.514 6 −66.392 1.000 42.731.834810 7 28.177 0.200 8 19.025 4.190 23.80 1.846660 9 −36.189 0.897 10−20.633 1.000 42.73 1.834810 11 −125.484 D11 (Variable) 12 −244.7251.512 42.73 1.834810 13 −35.967 D13 (Variable) 14 ∞ 2.000 (Stop S) 1511.692 7.246 82.57 1.497820 16 −15.635 0.800 23.80 1.846660 17 −55.0072.028 18 119.072 0.800 55.52 1.696800 19 30.792 1.886 20 46.232 7.36634.92 1.801000 21 −29.295 2.129 22 −9.299 1.000 35.72 1.902650 23−17.109 Bf [Various Data] f 18.500 34.176 53.500 Fno 3.606 4.649 5.743 ω38.474 21.695 14.318 Y 14.250 14.250 14.250 TL 84.418 96.972 109.393 Bf17.330 26.452 35.995 [Variable Distance Data] (Infinity) (ImagingDistance 1 m) Wide-Angle Telephoto Wide-Angle Telephoto End IntermediateEnd End Intermediate End f, β 18.500 34.176 53.500 −0.0196 −0.0358−0.0556 D0 0.000 0.000 0.000 915.6 903.0 890.6 D3 1.003 12.242 19.2871.003 12.242 19.287  D11 12.973 5.166 1.000 13.423 5.869 1.977  D133.717 3.717 3.717 3.266 3.013 2.739 [Lens Group Data] Group Group FirstGroup Focal Number Surface Length G1 1 89.519 G2 4 −14.853 G3 12 18.756[Conditional Expression Corresponding Value] Conditional Expression (1):f1/(−f2) = 6.03 Conditional Expression (2): (f32)/f3 = 3.19 ConditionalExpression (3): |f31|/f3 = 1.00 Conditional Expression (4): |f33|/f3 =8.00 Conditional Expression (5): ωw = 38.474 Conditional Expression (6):ft/fw = 2.89 Conditional Expression (7): f1/f3 = 4.77 ConditionalExpression (8): (f2)/f3 = 0.79 Conditional Expression (9): fw/f1 = 0.21Conditional Expression (10): fw/f3 = 0.99 Conditional Expression (11):f1/f3 = 4.77 Conditional Expression (12): (f32)/f3 = 3.19 ConditionalExpression (13): |f31|/f3 = 1.00 Conditional Expression (14): |f33|/f3 =8.00 Conditional Expression (15): ωw = 38.474 Conditional Expression(16): ft/fw = 2.89 Conditional Expression (17): (−f2)/f3 = 0.79Conditional Expression (18): f3A/f3 = 2.68 Conditional Expression (19):|f3B|/f3 = 1.64 Conditional Expression (20): |fvr|/f3 = 3.19 ConditionalExpression (21): ωw = 38.474 Conditional Expression (22): ft/fw = 2.89Conditional Expression (23): fw/f1 = 0.21 Conditional Expression (24):fw/f3 = 0.99 Conditional Expression (25): (−f32)/f3 = 3.19 ConditionalExpression (26): |f31|/f3 = 1.00 Conditional Expression (27): |f33|/f3 =8.00 Conditional Expression (28): ωw = 38.474 Conditional Expression(29): ft/fw = 2.89

Table 2 shows that the zoom optical system ZL2 according to Example 2satisfies the conditional expressions (1) to (29).

FIGS. 6A, 6B and 6C are graphs showing aberrations of the zoom opticalsystem ZL2 according to Example 2 in a wide-angle end state (f=18.500),in which FIG. 6A is graphs showing various aberrations upon focusing oninfinity, FIG. 6B is graphs showing various aberrations (imagingmagnification β=−0.0196) upon focusing on a short distant object, andFIG. 6C is graphs showing coma aberration when an image blur iscorrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS.7A, 7B and 7C are graphs showing aberrations of the zoom optical systemZL2 according to Example 2 in an intermediate focal length state(f=34.176), in which FIG. 7A is graphs showing various aberrations uponfocusing on infinity, FIG. 7B is graphs showing various aberrations(imaging magnification β=−0.0358) upon focusing on a short distantobject, and FIG. 7C is graphs showing coma aberration when an image bluris corrected (a correction angle θ=0.30°) upon focusing on infinity.FIGS. 8A, 8B and 8C are graphs showing aberrations of the zoom opticalsystem ZL2 according to Example 2 in a telephoto end state (f=53.500),in which FIG. 8A is graphs showing various aberrations upon focusing oninfinity, FIG. 8B is graphs showing various aberrations upon focusing ona short distant object (imaging magnification β=−0.0556), and FIG. 8C isgraphs showing coma aberration when an image blur is corrected (acorrection angle θ=0.30°) upon focusing on infinity. In the presentExample, as shown in FIG. 6C, FIG. 7C, and FIG. 8C, optical performanceupon vibration proofing is shown in graphs showing coma aberration,centering on an image height y=0.0, corresponding to image heights ofvertically plus 10.0 and minus 10.0.

From each of the graphs showing aberration shown in FIGS. 6A-6C, 7A-7Cand 8A-8C, the zoom optical system ZL2 according to Example 2 is foundto have high imaging performance in which various aberrations aresuccessfully corrected from the wide-angle end state to the telephotoend. Moreover, the zoom optical system ZL2 is found to have high imagingperformance also upon correcting the image blur.

(Example 3)

Example 3 will be described using FIG. 9, FIGS. 10A-10C, 11A-11C,12A-12C and Table 3. As shown in FIG. 9, a zoom optical system ZL (ZL3)according to Example 3 is configured of, disposed in order from anobject along an optical axis, a first lens group G1 having positiverefractive power, a second lens group G2 having negative refractivepower, and a third lens group G3 having positive refractive power.

The first lens group G1 is configured of, disposed in order from theobject, a cemented lens formed by cementing a negative meniscus lens L11having a convex surface facing the object and a biconvex lens L12.

The second lens group G2 is configured of, disposed in order from theobject, a negative meniscus lens L21 having a convex surface facing theobject, a biconcave lens L22, and a positive meniscus lens L23 having aconvex surface facing the object. A surface of the negative meniscuslens L21 to the object is aspherical.

The third lens group G3 is configured of, disposed in order from theobject, a 31st lens group G31, a 32nd lens group G32, and a 33rd lensgroup G33.

The 31st lens group G31 is configured of, disposed in order from theobject, a front group G3F having positive refractive power and a reargroup G3R. The front group G3F (focusing group) is configured of abiconvex lens L31. The rear group G3R is configured of, disposed inorder from the object, a cemented lens formed by cementing a biconvexL32 and a negative meniscus lens L33 having a concave surface facing theobject.

The 32nd lens group G32 (vibration-proof lens group) is configured of anegative meniscus lens L34 having a convex surface facing the object.The 33rd lens group G33 is configured of, disposed in order from theobject, a biconvex lens L35, and a negative meniscus lens L36 having aconcave surface facing the object. A surface of the negative meniscuslens L34 to the object is aspherical. A surface of the negative meniscuslens L36 to the object is aspherical.

An aperture stop S determining an F-number is provided within the thirdlens group G3.

An image surface I is formed on an imaging element (not shown), and theimaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL3 according to Example 3, zooming from awide-angle end state to a telephoto end state is made by varying an airdistance between the first lens group G1 and the second lens group G2and an air distance between the second lens group G2 and the third lensgroup G3. At this time, relative to the image surface I, the first lensgroup G1 monotonously moves to the object. The second lens group G2monotonously moves to the object. The third lens group G3 monotonouslymoves to the object. The aperture stop S monotonously moves to theobject integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL3 according to Example3, zooming from the wide-angle end state to the telephoto end state ismade by moving each of the lens groups G1 to G3 along the optical axisin such a manner that the air distance between the first lens group G1and the second lens group G2 is enlarged, and the air distance betweenthe second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL3 according to Example 3 has a configurationin which focusing is made by moving the front group G3F of the thirdlens group G3, namely the biconvex lens L31 along the optical axisdirection, and as shown by an arrow in FIG. 9, upon causing a changefrom a state of focusing on infinity to a state of focusing on shortdistant object, the biconvex lens L31 moves from the object to an image.

Upon occurrence of an image blur, correction of the image blur(vibration proofing) on the image surface I is made by moving, as avibration-proof lens group, the 32nd lens group G32, namely the negativemeniscus lens L34 having the convex surface facing the object so as tohave a component in a direction perpendicular to the optical axis.

Table 3 below shows values of each of specifications in Example 3.Surface numbers 1 to 22 in Table 3 correspond to optical surfaces m1 tom22 shown in FIG. 9, respectively

TABLE 3 [Lens Data] Surface Number r D νd nd  1 54.753 1.500 23.801.846660  2 38.695 5.554 67.90 1.593190  3 −34295.201  D3 (Variable) *478.694 0.160 38.09 1.553890  5 98.152 1.200 42.73 1.834810  6 10.8473.606  7 −970.417 1.000 42.73 1.834810  8 23.052 1.059  9 17.651 2.71825.45 1.805180 10 124.240 D10 (Variable) 11 756.198 1.530 44.80 1.74400012 −42.339 D12 (Variable) 13 ∞ 2.000 (Stop S) 14 10.744 4.744 82.571.497820 15 −14.187 0.800 32.35 1.850260 16 −36.052 2.298 *17  61.1670.800 49.26 1.743200 18 25.724 3.680 19 40.116 2.998 36.40 1.620040 20−27.927 2.317 *21  −8.706 1.000 31.27 1.903660 22 −17.386 Bf [AsphericalSurface Data] The 4th Surface K = 1.0000 A4 = −8.92993E−06 A6 =−3.84277E−08 A8 = 5.03368E−10 A10 = −1.64069E−12 The 17th Surface K =1.0000 A4 = 4.87068E−06 A6 = −6.89267E−08 A8 = 0.00000E+00 A10 =0.00000E+00 The 21st Surface K = 1.0000 A4 = −3.24561E−05 A6 =−9.10280E−07 A8 = 2.25192E−08 A10 = −6.24358E−10 [Various Data] f 18.47734.000 53.500 Fno 3.630 4.663 5.630 ω 39.444 21.946 14.295 Y 14.25014.250 14.250 TL 74.395 88.467 104.339 Bf 17.318 26.476 34.918 [VariableDistance Data] (Infinity) (Imaging Distance 1 m) Wide-Angle TelephotoWide-Angle Telephoto End Intermediate End End Intermediate End f, β18.477 34.000 53.500 −0.0194 −0.0355 −0.0552 D0 0.000 0.000 0.000 925.6911.5 895.7 D3 1.000 14.075 25.532 1.000 14.075 25.532  D10 13.187 5.0261.000 13.679 5.760 2.066  D12 3.919 3.919 3.919 3.428 3.185 2.852 [LensGroup Data] Group Group First Group Focal Number Surface Length G1 1110.968 G2 4 −16.768 G3 11 18.415 [Conditional Expression CorrespondingValue] Conditional Expression (1): f1/(−f2) = 6.62 ConditionalExpression (2): (−f32)/f3 = 3.28 Conditional Expression (3): |f31|/f3 =0.93 Conditional Expression (4): |f33|/f3 = 7.37 Conditional Expression(5): ωw = 39.444 Conditional Expression (6): ft/fw = 2.90 ConditionalExpression (7): f1/f3 = 6.03 Conditional Expression (8): (−f2)/f3 = 0.91Conditional Expression (9): fw/f1 = 0.17 Conditional Expression (10):fw/f3 = 1.00 Conditional Expression (11): f1/f3 = 6.03 ConditionalExpression (12): (−f32)/f3 = 3.28 Conditional Expression (13): |f31|/f3= 0.93 Conditional Expression (14): |f33|/f3 = 7.37 ConditionalExpression (15): ωw = 39.444 Conditional Expression (16): ft/fw = 2.90Conditional Expression (17): (−f2)/f3 = 0.91 Conditional Expression(18): f3A/f3 = 2.93 Conditional Expression (19): |f3B|/f3 = 1.63Conditional Expression (20): |fvr|/f3 = 3.28 Conditional Expression(21): ωw = 39.444 Conditional Expression (22): ft/fw = 2.90 ConditionalExpression (23): fw/f1 = 0.17 Conditional Expression (24): fw/f3 = 1.00Conditional Expression (25): (−f32)/f3 = 3.28 Conditional Expression(26): |f31|/f3 = 0.93 Conditional Expression (27): |f33|/f3 = 7.37Conditional Expression (28): ωw = 39.444 Conditional Expression (29):ft/fw = 2.90

Table 3 shows that the zoom optical system ZL3 according to Example 3satisfies the conditional expressions (1) to (29).

FIGS. 10A, 10B and 10C are graphs showing aberrations of the zoomoptical system ZL3 according to Example 3 in a wide-angle end state(f=18.477), in which FIG. 10A is graphs showing various aberrations uponfocusing on infinity, FIG. 10B is graphs showing various aberrationsupon focusing on a short distant object (imaging magnificationβ=−0.0194), and FIG. 10C is graphs showing coma aberration when an imageblur is corrected (a correction angle θ=0.30°) upon focusing oninfinity. FIGS. 11A, 11B and 11C are graphs showing aberrations of thezoom optical system ZL3 according to Example 3 in an intermediate focallength state (f=34.000), in which FIG. 11A is graphs showing variousaberrations upon focusing on infinity, FIG. 11B is graphs showingvarious aberrations upon focusing on a short distant object (imagingmagnification β=−0.0355), and FIG. 11C is graphs showing coma aberrationwhen an image blur is corrected (a correction angle θ=0.30°) uponfocusing on infinity. FIGS. 12A, 12B and 12C are graphs showingaberrations of the zoom optical system ZL3 according to Example 3 in atelephoto end state (f=53.500), in which FIG. 12A is graphs showingvarious aberrations upon focusing on infinity, FIG. 12B is graphsshowing various aberrations upon focusing on a short distant object(imaging magnification β=−0.0552), and FIG. 12C is graphs showing comaaberration when an image blur is corrected (a correction angle θ=0.30°)upon the focusing on infinity. In the present Example, as shown in FIG.10C, FIG. 11C and FIG. 12C, optical performance upon vibration proofingis shown in graphs showing coma aberration, centering on an image heighty=0.0, corresponding to image heights of vertically plus 10.0 and minus10.0.

From each of the graphs showing aberration shown in FIGS. 10A-10C,11A-11C and 12A-12C, the zoom optical system ZL3 according to Example 3is found to have high imaging performance in which various aberrationsare successfully corrected from the wide-angle end state to thetelephoto end. Moreover, the zoom optical system ZL3 is found to havehigh imaging performance also upon correcting the image blur.

(Example 4)

Example 4 will be described using FIG. 13, FIGS. 14A-14C, 15A-15C,16A-16C and Table 4. As shown in FIG. 13, a zoom optical system ZL (ZL4)according to Example 4 is configured of, disposed in order from anobject along an optical axis, a first lens group G1 having positiverefractive power, a second lens group G2 having negative refractivepower, a third lens group G3 having positive refractive power, and afourth lens group G4 having positive refractive power.

The first lens group G1 is configured of, disposed in order from theobject, a cemented lens formed by cementing a negative meniscus lens L11having a convex surface facing the object, and a biconvex lens L12.

The second lens group G2 is configured of, disposed in order from theobject, a negative meniscus lens L21 having a convex surface facing theobject, a biconcave lens L22, and a positive meniscus lens L23 having aconvex surface facing the object. A surface of the negative meniscuslens L21 to the object is aspherical.

The third lens group G3 is configured of, disposed in order from theobject, a 31st lens group G31, a 32nd lens group G32, and a 33rd lensgroup G33.

The 31st lens group G31 is configured of, disposed in order from theobject, a front group G3F having positive refractive power and a reargroup G3R. The front group G3F (focusing group) is configured of abiconvex lens L31, The rear group G3R is configured of, disposed inorder from the object, a cemented lens formed by cementing a biconvexlens L32 and a biconcave lens L33.

The 32nd lens group G32 (vibration-proof lens group) is configured of anegative meniscus lens L34 having a convex surface facing the object.The 33rd lens group G33 is configured of, disposed in order from theobject, a biconvex lens L35 and a biconcave lens L36. A surface of thenegative meniscus lens L36 to the object is aspherical.

The fourth lens group G4 is configured of a biconvex lens L41.

An aperture stop S determining an F-number is provided within the thirdlens group G3.

An image surface I is formed on an imaging element (not shown), and theimaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL4 according to Example 4, zooming from awide-angle end state to a telephoto end state is made by varying an airdistance between the first lens group G1 and the second lens group G2,an air distance between the second lens group G2 and the third lensgroup G3, and an air distance between the third lens group G3 and thefourth lens group G4. At this time, relative to the image surface I, thefirst lens group G1 monotonously moves to the object. The second lensgroup G2 monotonously moves to a direction of the object. The third lensgroup G3 monotonously moves to the object. The fourth lens group G4monotonously moves to the object. The aperture stop S monotonously movesto the object integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL4 according to Example4, zooming from the wide-angle end state to the telephoto end state ismade by moving each of the lens groups G1 to G4 along the optical axisin such a manner that the air distance between the first lens group G1and the second lens group G2 is enlarged, the air distance between thesecond lens group G2 and the third lens group G3 is reduced, and the airdistance between the third lens group G3 and a fourth lens group G4 isenlarged.

The zoom optical system ZL4 according to Example 4 has a configurationin which focusing is made by moving the front group G3F of the thirdlens group G3, namely the biconvex lens L31 along the optical axisdirection, and as shown by an arrow in FIG. 13, upon causing a changefrom a state of focusing on infinity to a state of focusing in a shortdistant object, the biconvex lens L31 moves from the object to an image.

Upon occurrence of an image blur, correction of the image blur(vibration proofing) on the image surface I is made by moving, as avibration-proof lens group, the 32nd lens group G32, namely the negativemeniscus lens L34 having the convex surface facing the object so as tohave a component in a direction perpendicular to the optical axis.

Table 4 below shows values of each of specifications in Example 4.Surface numbers 1 to 23 in Table 4 correspond to optical surfaces m1 tom23 shown in FIG. 13, respectively.

TABLE 4 [Lens Data] Surface Number r D νd nd  1 67.912 1.500 42.731.834810  2 44.077 4.405 67.90 1.593190  3 −288.500 D3 (Variable) *433.454 1.200 42.73 1.834810  5 10.199 4.749  6 −36.627 1.000 50.271.719990  7 36.778 0.404  8 19.164 2.419 23.80 1.846660  9 95.617 D9(Variable) 10 89.310 1.766 65.44 1.603000 11 −30.641 D11 (Variable)  12∞ 2.000 (Stop S) 13 9.587 3.001 58.54 1.612720 14 −1767.044 1.000 23.801.846660 15 20.932 2.301 16 151.332 1.699 82.57 1.497820 17 24.318 1.80518 16.814 3.077 69.89 1.518600 19 −24.653 1.282 *20  −12.479 1.000 35.721.902650 21 194.680 D21 (Variable)  22 41.253 2.502 23.80 1.846660 23−90.972 Bf [Aspherical Surface Data] The 4th Surface K = 1.0000 A4 =−1.31511E−05 A6 = −1.12654E−07 A8 = 7.35232E−10 A10 = −2.69203E−12 The20th Surface K = 1.0000 A4 = −1.69994E−04 A6 = −2.07858E−06 A8 =6.76235E−09 A10 = −8.84176E−10 [Various Data] f 18.500 34.061 53.500 Fno3.568 4.700 5.851 ω 39.495 21.888 14.364 Y 14.250 14.250 14.250 TL74.382 87.897 104.318 Bf 17.380 27.437 37.937 [Variable Distance Data](Infinity) (Imaging Distance 1 m) Wide-Angle Telephoto Wide-AngleTelephoto End Intermediate End End Intermediate End f, β 18.500 34.06153.500 −0.0194 −0.0355 −0.0556 D0 0.000 0.000 0.000 925.6 912.1 895.7 D31.000 12.968 22.438 1.000 12.968 22.438 D9 14.194 5.413 1.000 14.6716.042 1.837  D11 3.342 3.342 3.342 2.865 2.712 2.504  D21 1.346 1.6172.481 1.346 1.617 2.481 [Lens Group Data] Group Group First Group FocalNumber Surface Length G1 1 112.838 G2 4 −17.024 G3 10 20.227 G4 2233.817 [Conditional Expression Corresponding Value] ConditionalExpression (11): f1/f3 = 5.58 Conditional Expression (12): (−f32)/f3 =2.89 Conditional Expression (13): |f31|/f3 = 0.92 Conditional Expression(14): |f33|/f3 = 2.97 Conditional Expression (15): ωw = 39.495Conditional Expression (16): ft/fw = 2.89 Conditional Expression (23):fw/f1 = 0.16 Conditional Expression (24): fw/f3 = 0.91 ConditionalExpression (25): (−f32)/f3 = 2.89 Conditional Expression (26): |f31|/f3= 0.92 Conditional Expression (27): |f33|/f3 = 2.97 ConditionalExpression (28): ωw = 39.495 Conditional Expression (29): ft/fw = 2.89

Table 4 shows that the zoom optical system ZL4 according to Example 4satisfies the conditional expressions (11) to (16) and (23) to (28).

FIGS. 14A, 14B and 14C are graphs showing aberrations of the zoomoptical system ZL4 according to Example 4 in a wide-angle end state(f=18.500), in which FIG. 14A is graphs showing various aberrations uponfocusing on infinity, FIG. 14B is graphs showing various aberrationsupon focusing on a short distant object (imaging magnificationβ=−0.0194), and FIG. 14C is graphs showing coma aberration when an imageblur is corrected (a correction angle θ: 30°) upon focusing on infinity.FIGS. 15A, 15B and 15C are graphs showing aberrations of the zoomoptical system ZL4 according to Example 4 in an intermediate focallength state (f=34.061), in which FIG. 15A is graphs showing variousaberrations upon focusing on infinity, FIG. 15B is graphs showingvarious aberrations upon focusing on a short distant object (imagingmagnification β=−0.0355), and FIG. 15C is graphs showing coma aberrationwhen an image blur is corrected (a correction angle θ=0.30°) uponfocusing on infinity. FIGS. 16A, 16B and 16C are graphs showingaberrations of the zoom optical system ZL4 according to Example 4 in atelephoto end state (f=53.500), in which FIG. 16A is graphs showingvarious aberrations upon focusing on infinity, FIG. 16B is graphsshowing various aberrations upon focusing on a short distant object(imaging magnification β=−0.0556), and FIG. 16C is graphs showing comaaberration when an image blur is corrected (a correction angle θ=0.30°)upon focusing on infinity. In the present example, as shown in FIG. 14C,FIG. 15C, and FIG. 16C, optical performance upon vibration proofing isshown in graphs showing coma aberration, centering on an image heighty=0.0, corresponding to image heights of vertically plus 10.0 and minus10.0.

From each of the graphs showing aberration shown in FIGS. 14A-14C,15A-15C and 16A-16C, the zoom optical system ZL4 according to Example 4is found to have high imaging performance in which various aberrationsare successfully corrected from the wide-angle end state to thetelephoto end. Moreover, the zoom optical system ZL4 is found to havehigh imaging performance also upon correcting the image blur.

According to each Example described above, while the zoom optical systemis provided with an image blur correction mechanism, the zoom opticalsystem has high optical performance can be realized.

In addition, each Example described above shows one specific example ofthe zoom optical system according to each of the first to fourthembodiments, and the zoom optical systems according to the first tofourth embodiments are not limited thereto. In the first to fourthembodiments, the following content can be appropriately adopted withinthe range in which the optical performance is not adversely affected.

In Examples using numerical values according to the first to fourthembodiments, a three-group configuration was shown. However, the presentinvention can also be applied to other configurations such as afour-group configuration. For example, a configuration in which a lensor lens group is added thereto on a side closest to the object, or aconfiguration is allowed in which a lens or lens group is added theretoon a side closest to the image. Moreover, the lens group represents apart which is separated by the air distances which change upon zoomingor focusing and have at least one lens.

In the first to fourth embodiments, the zoom optical system may beformed into a focusing lens group in which focusing on an infinitedistant object to a short distant object is made by moving a single lensgroup or a plurality of lens groups, or a partial lens group in theoptical axis direction. The focusing lens group can also be applied toautofocusing, and is also suitable for a motor drive (using anultrasonic motor, or the like) for autofocusing. In particular, at leasta part of the third lens group G3 is preferably applied as the focusinglens group.

In the first to fourth embodiments, the zoom optical system may beformed into the vibration-proof lens group in which the image blurcaused by camera shake is corrected by moving the lens group or thepartial lens group so as to have the component in the directionperpendicular to the optical axis, or rotationally moving (swinging) thelens group or the partial lens group in an in-plane direction includingthe optical axis. In particular, at least a part of the third lens groupG3 is preferably applied as the vibration-proof lens group.

In the first to fourth embodiments, a lens surface may be formed of aspherical surface or a flat surface, or formed of an aspherical surface.When the lens surface is spherical or flat, lens processing and assemblyand adjustment are facilitated, and deterioration of optical performanceby an error of the processing and assembly and adjustment can beprevented. Thus, such a case is preferable. Moreover, when the lenssurface is aspherical, the aspherical surface may be any asphericalsurface, including an aspherical surface by grinding, a glass moldaspherical surface in which glass is formed into an aspherical surfaceshape by using a mold, and a composite type aspherical surface in whicha resin is formed into the aspherical surface shape on a surface ofglass. Moreover, the lens surface may be formed into a diffractionsurface, or the lens may be formed into a gradient index lens (GRINlens) or a plastic lens.

In the first to fourth embodiments, the aperture stop S is preferablyarranged in a neighborhood of the third lens group G3 or within thethird lens group G3. However, a lens frame may be used as substitutionfor such a role without providing a member as the aperture stop.

In the first to fourth embodiments, an antireflection film having hightransmittance in a wide wavelength range may be applied to each lenssurface in order to reduce a flare and a ghost to achieve high opticalperformance with high contrast.

The zoom optical systems ZL according to the first to fourth embodimentseach have a zoom ratio of about 2 to 7.

Description of the Embodiments (Fifth and Sixth Embodiments)

Hereinafter, a fifth embodiment will be described with reference todrawings. As shown in FIG. 22, a zoom optical system ZL according to thefifth embodiment has, disposed in order from an object, a first lensgroup G1 having positive refractive power, a second lens group G2 havingnegative refractive power, and a third lens group G3 having positiverefractive power.

According to this configuration, size reduction of a lens barrel can beachieved and variations in aberration upon zooming can be successfullycorrected.

Moreover, in the zoom optical system ZL, focusing is made by moving, asa focusing lens group, at least a part of the third lens group G3 (forexample, a biconvex lens L31 in FIG. 22) along an optical axisdirection.

According to this configuration, size reduction of the lens barrel canbe achieved and variations in aberration (for example, sphericalaberration, curvature of field, and the like) upon focusing can besuccessfully corrected.

Under the configuration, the zoom optical system ZL satisfies thefollowing conditional expression (30):0.90<f3/fw<1.50  (30)

where f3 denotes a focal length of the third lens group G3, and

fw denotes a focal length of the zoom optical system in a wide-angle endstate.

The conditional expression (30) specifies a ratio of the focal length f3of the third lens group G3 to the focal length fw of the zoom opticalsystem in the wide-angle end state. In the present zoom optical systemZL, size reduction of the lens barrel and successful optical performancecan be realized by satisfying the conditional expression (30).

If the ratio thereof is more than an upper limit of the conditionalexpression (30), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. Refractivepower of the first lens group G1 and the second lens group G2 is to beincreased in order to achieve size reduction, and correction of comaaberration, astigmatism, and curvature of field becomes difficult. Ifthe ratio thereof is less than a lower limit of the conditionalexpression (30), refractive power of the third lens group G3 increases,and correction of spherical aberration, coma aberration, and astigmatismbecomes difficult.

Further successful aberration correction can be made by setting thelower limit of the conditional expression (30) to 1.00.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (30) to 1.35.

In the zoom optical system ZL according to the fifth embodiment, zoomingis preferably made by varying an air distance between the first lensgroup G1 and the second lens group G2 and an air distance between thesecond lens group G2 and the third lens group G3.

According to this configuration, spherical aberration and curvature offield caused upon zooming can be successfully corrected.

In the zoom optical system ZL according to the fifth embodiment, uponzooming from the wide-angle end state to the telephoto end state, theair distance between the first lens group G1 and the second lens groupG2 is preferably enlarged, and the air distance between the second lensgroup G2 and the third lens group G3 is preferably reduced.

According to this configuration, spherical aberration and curvature offield caused upon zooming can be successfully corrected.

The zoom optical system ZL according to the fifth embodiment preferablysatisfies the following conditional expression (31):4.70<f1/f3<30.00  (31)

where f1 denotes a focal length of the first lens group G1.

The conditional expression (31) specifies a ratio of the focal length f1of the first lens group G1 to the focal length f3 of the third lensgroup G3. In the present zoom optical system ZL, size reduction of thelens barrel and a predetermined zoom ratio can be realized by satisfyingthe conditional expression (31).

If the ratio thereof is more than an upper limit of the conditionalexpression (31), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult. If the ratio thereof is less thana lower limit of the conditional expression (31), refractive power ofthe first lens group G1 increases, and correction of coma aberration,astigmatism, and curvature of field in the telephoto end state becomesdifficult.

Further successful aberration correction can be made by setting thelower limit of the conditional expression (31) to 4.76.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (31) to 10.00.

The zoom optical system ZL according to the fifth embodiment preferablysatisfies the following conditional expression (32):0.60<(−f2)/f3<1.05  (32)

where f2 denotes a focal length of the second lens group G2.

The conditional expression (32) specifies a ratio of the focal length f3of the third lens group G3 to the focal length f2 of the second lensgroup G2. In the present zoom optical system ZL, successful opticalperformance and a predetermined zoom ratio can be realized by satisfyingthe conditional expression (32).

If the ratio thereof is more than an upper limit of the conditionalexpression (32), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult. If the ratio thereof is less thana lower limit of the conditional expression (32), refractive power ofthe second lens group G2 increases, and correction of coma aberrationand astigmatism in the wide-angle end state becomes difficult.

Further successful aberration correction can be made by setting thelower limit of the conditional expression (32) to 0.70.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (32) to 1.00.

The zoom optical system ZL according to the fifth embodiment preferablysatisfies the following conditional expression (33):5.20<f1/(−f2)<30.00  (33)

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

The conditional expression (33) specifies a ratio of the focal length f1of the first lens group G1 to the focal length f2 of the second lensgroup G2. In the present zoom optical system ZL, successful opticalperformance and a predetermined zoom ratio can be realized by satisfyingthe conditional expression (33).

If the ratio thereof is more than an upper limit of the conditionalexpression (33), refractive power of the second lens group G2 increases,and correction of coma aberration and astigmatism in the wide-angle endstate becomes difficult. If the ratio thereof is less than a lower limitof the conditional expression (33), refractive power of the first lensgroup G1 increases, and correction of coma aberration, astigmatism, andcurvature of field in the telephoto end state becomes difficult.

Further successful aberration correction can be made by setting thelower limit of the conditional expression (33) to 5.30.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (33) to 10.00.

In the zoom optical system ZL according to the fifth embodiment, atleast a part of the third lens group G3 (for example, a positivemeniscus lens L34 having a convex surface facing the object in FIG. 22)is preferably configured to be movable, as a vibration-proof lens groupfor correcting an image blur, so as to have a component in a directionperpendicular to the optical axis.

According to this configuration, variations in curvature of field andvariations in decentering coma aberration upon correcting the image blurcan be simultaneously corrected.

In the zoom optical system ZL according to the fifth embodiment, thefirst lens group G1 is preferably formed of one cemented lens.

According to this configuration, while size reduction of the lens barrelis achieved, lateral chromatic aberration in the telephoto end state canbe successfully corrected.

In the zoom optical system ZL according to the fifth embodiment, thesecond lens group G2 is preferably formed of two negative lenses and onepositive lens.

According to this configuration, coma aberration and curvature of fieldin the wide-angle end state can be successfully corrected.

In the zoom optical system ZL according to the fifth embodiment, thesecond lens group G2 is preferably formed of, disposed in order from theobject, a negative lens, a negative, lens, and a positive lens.

According to this configuration, coma aberration and curvature of fieldin the wide-angle end state can be successfully corrected.

In the zoom optical system ZL according to the fifth embodiment, thethird lens group G3 is preferably formed of six or more lenses.

According to this configuration, spherical aberration and comaaberration can be successfully corrected.

The zoom optical system ZL according to the fifth embodiment preferablysatisfies the following conditional expression (34):30.00°<ωw<80.00°  (34)

where ωw denotes a half angle of view in the wide-angle end state.

The conditional expression (34) represents a condition specifying avalue of an angle of view in the wide-angle end state. While the zoomoptical system ZL has a wide angle of view, coma aberration, distortion,and curvature of field can be successfully corrected by satisfying theconditional expression (34).

Further successful aberration correction can be made by setting a lowerlimit of the conditional expression (34) to 33.00°. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (34) to 36.00°.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (34) to 77.00°.

The zoom optical system ZL according to the fifth embodiment preferablysatisfies the following conditional expression (35):2.00<ft/fw<15.00  (35)

where ft denotes a focal length of the zoom optical system in thetelephoto end state.

The conditional expression (35) represents a condition specifying aratio of the focal length of the zoom optical system in the telephotoend state to the focal length of the zoom optical system in thewide-angle end state. In the present zoom optical system ZL, a high zoomratio can be obtained, and simultaneously spherical aberration and comaaberration can be successfully corrected by satisfying the conditionalexpression (35).

Further successful aberration correction can be made by setting a lowerlimit of the conditional expression (35) to 2.30. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (35) to 2.50. An effect of the fifthembodiment can be exhibited to a maximum by setting the lower limit ofthe conditional expression (35) to 2.70.

Further successful aberration correction can be made by setting an upperlimit of the conditional expression (35) to 10.00. Still furthersuccessful aberration correction can be made by setting the upper limitof the conditional expression (35) to 7.00.

As shown in FIG. 22 and FIG. 26, in the zoom optical system ZL accordingto the fifth embodiment, a focusing lens group is preferably arranged,in the third lens group G3, on a side closer to the object than thevibration-proof lens group. At this time, the focusing lens group ispreferably arranged, in the third lens group G3, on a side closest tothe object. Moreover, the focusing lens group is preferably formed of asingle lens.

As shown in FIG. 30, in the zoom optical system ZL according to thefifth embodiment, the vibration-proof lens group is preferably arranged,in the third lens group G3, on a side closer to the object than thefocusing lens group. At this time, the vibration-proof lens group ispreferably arranged, in the third lens group G3, on a side closest tothe object. Moreover, the vibration-proof lens group is preferablyformed of a single lens.

According to the fifth embodiment as described above, the zoom opticalsystem ZL having successful optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoomoptical system ZL will be described with reference to FIG. 34. As shownin FIG. 34, the camera 1 is a lens interchangeable camera (so-calledmirrorless camera) provided with the above-mentioned zoom optical systemZL as an imaging lens 2.

In the camera 1, light from an object (subject) (not shown) is collectedby the imaging lens 2 to form a subject image on an imaging surface ofan imaging unit 3 through an OLPF (optical low pass filter) (not shown).The subject image is then subjected to photoelectric conversion by aphotoelectric conversion element provided in the imaging unit 3 toproduce an image of the subject. This image is displayed on an EVF(electronic view finder) 4 provided in the camera 1. Thus, aphotographer can observe the subject through the EVF4.

Moreover, if a release bottom (not shown) is pressed by thephotographer, the image of the subject produced in the imaging unit 3 isstored in a memory (not shown). Thus, the photographer can photographthe subject by the camera 1.

As is known also from each Example described later, the zoom opticalsystem ZL according to the fifth embodiment, mounted in the camera 1 asthe imaging lens 2, has successful optical performance by thecharacteristic lens configuration. Thus, according to the present camera1, the imaging device having successful optical performance can berealized.

In addition, even when the above-mentioned zoom optical system ZL ismounted on a single-lens reflex camera that has a quick return mirrorand observes the subject by a finder optical system, an effect similarto the effect of the camera 1 can be produced. Moreover, even when theabove-mentioned zoom optical system ZL is mounted on a video camera, aneffect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZLhaving the configuration will be generally described with reference toFIG. 35. First, each lens is arranged within a lens barrel in such amanner that a zoom optical system ZL has a first lens group G1 havingpositive refractive power, a second lens group G2 having negativerefractive power, and a third lens group G3 having positive refractivepower (step ST510). At this time, each lens is arranged within the lensbarrel in such a manner that focusing is made by moving at least a partof the third lens group G3 along an optical axis direction as a focusinglens group (step ST520). Each lens is arranged within the lens barrel insuch a manner that at least the following conditional expression (30) issatisfied among the conditional expressions (step ST530):0.90<f3/fw<1.50  (30)

where f3 denotes a focal length of the third lens group G3, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

To take a lens arrangement according to the fifth embodiment as oneexample, as shown in FIG. 22, as the first lens group G1, in order fromthe object, a cemented positive lens formed by cementing a negativemeniscus lens L11 having a convex surface facing the object and abiconvex lens L12 is arranged. As the second lens group G2, in orderfrom the object, a negative meniscus lens L21 having a convex surfacefacing the object, a biconcave lens L22, and a positive meniscus lensL23 having a convex surface facing the object are arranged. As the thirdlens group G3, in order from the object, a biconvex lens L31, a cementedpositive lens formed by cementing a biconvex lens L32 and a biconcavelens L33, a positive meniscus lens L34 having a convex surface facingthe object, a biconvex lens L35, and a negative meniscus lens L36 havinga convex surface facing the image are arranged. Moreover, each lens isarranged in such a manner that the conditional expression (30) (acorresponding value of the conditional expression (30) is 1.14) issatisfied.

In addition, in the manufacturing method, each lens is preferablyarranged within the lens barrel in such a manner that at least a part ofthe third lens group G3 (for example, the positive meniscus lens L34having the convex surface facing the object in FIG. 22) is movable, as avibration-proof lens group for correcting the image blur, so as to havea component in a direction perpendicular to the optical axis.

Moreover, in the manufacturing method, each lens is preferably arrangedwithin the lens barrel in such a manner that the focusing lens group isarranged, in the third lens group G3, on a side closer to the objectthan the vibration-proof lens group (see FIG. 22 and FIG. 26).

Moreover, in the manufacturing method, each lens is preferably arrangedwithin the lens barrel in such a manner that the vibration-proof lensgroup is arranged, in the third lens group G3, on a side closer to theobject than the focusing group (see FIG. 30).

According to the method for manufacturing the zoom optical systemrelated to the fifth embodiment as described above, the zoom opticalsystem ZL having successful optical performance can be obtained.

Next, a sixth embodiment will be described with reference to drawings.As shown in FIG. 22, a zoom optical system ZL according to the sixthembodiment has, disposed in order from an object, a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a third lens group G3 having positive refractivepower.

According to this configuration, size reduction of the lens barrel canbe realized and variations in aberration upon zooming can besuccessfully corrected.

Moreover, the zoom optical system ZL has a configuration in which atleast a part of the third lens group G3 (for example, the positivemeniscus lens L34 having the convex surface facing the object in FIG.22) is movable, as a vibration-proof lens group for correcting the imageblur, so as to have a component in a direction perpendicular to theoptical axis.

According to this configuration, variations in curvature of field andvariations in decentering coma upon correcting the image blur can besimultaneously corrected.

Under the configuration, the zoom optical system ZL satisfies thefollowing conditional expression (36):0.60<f3/fw<3.50  (36)

where f3 denotes a focal length of the third lens group G3, and

fw denotes a focal length of the zoom optical system in a wide-angle endstate.

The conditional expression (36) specifies a ratio of the focal length f3of the third lens group G3 to the focal length fw of the zoom opticalsystem in the wide-angle end state. In the present zoom optical systemZL, size reduction of the lens barrel and successful optical performancecan be realized by satisfying the conditional expression (36).

If the ratio thereof is more than an upper limit of the conditionalexpression (36), refractive power of the third lens group G3 is reduced,and size reduction of the lens barrel becomes difficult. Refractivepower of the first lens group G1 and the second lens group G2 is to beincreased in order to achieve size reduction, and correction of comaaberration, astigmatism, and curvature of field becomes difficult. Ifthe ratio thereof is less than a lower limit of the conditionalexpression (36), refractive power of the third lens group G3 increases,and correction of spherical aberration, coma aberration, and astigmatismbecomes difficult.

Further successful aberration correction can be made by setting thelower limit of the conditional expression (36) to 0.75. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (36) to 0.85.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (36) to 2.00. Still furthersuccessful aberration correction can be made by setting the upper limitof the conditional expression (36) to 1.50.

In the zoom optical system ZL according to the sixth embodiment, zoomingis preferably made by varying an air distance between the first lensgroup G1 and the second lens group G2 and an air distance between thesecond lens group G2 and the third lens group G3.

According to this configuration, spherical aberration and curvature offield caused upon zooming can be successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, uponzooming from the wide-angle end state to the telephoto end state, theair distance between the first lens group G1 and the second lens groupG2 is preferably enlarged, and the air distance between the second lensgroup G2 and the third lens group G3 is preferably reduced.

According to this configuration, spherical aberration and curvature offield caused upon zooming can be successfully corrected.

The zoom optical system ZL according to the sixth embodiment preferablysatisfies the following conditional expression (37):4.70<f1/f3<30.00  (37)

where f1 denotes a focal length of the first lens group G1.

The conditional expression (37) specifies a ratio of the focal length f1of the first lens group G1 to the focal length f3 of the third lensgroup G3. In the present zoom optical system, ZL size reduction of thelens barrel and a predetermined zoom ratio can be realized by satisfyingthe conditional expression (37).

If the ratio thereof is more than an upper limit of the conditionalexpression (37), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult. If the ratio thereof is less thana lower limit of the conditional expression (37), refractive power ofthe first lens group G1 increases, and correction of coma aberration,astigmatism, and curvature of field in the telephoto end state becomesdifficult.

Further successful aberration correction can be made by setting thelower limit of the conditional expression (37) to 4.76.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (37) to 10.00.

The zoom optical system ZL according to the sixth embodiment preferablysatisfies the following conditional expression (38):0.60<(−f2)/f3<1.05  (38)

where f2 denotes a focal length of the second lens group G2.

The conditional expression (38) specifies a ratio of the focal length f3of the third lens group G3 to the focal length f2 of the second lensgroup G2. In the present zoom optical system ZL, successful opticalperformance and a predetermined zoom ratio can be realized by satisfyingthe conditional expression (38).

If the ratio thereof is more than an upper limit of the conditionalexpression (38), refractive power of the third lens group G3 increases,and correction of spherical aberration and coma aberration in thetelephoto end state becomes difficult. If the ratio thereof is less thana lower limit of the conditional expression (38), refractive power ofthe second lens group G2 increases, and correction of coma aberrationand astigmatism in the wide-angle end state becomes difficult.

Further successful aberration correction can be made by setting thelower limit of the conditional expression (38) to 0.70.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (38) to 1.00.

The zoom optical system ZL according to the sixth embodiment preferablysatisfies the following conditional expression (39):5.20<f1/(−f2)<30.00  (39)

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

The conditional expression (39) specifies a ratio of the focal length f1of the first lens group G1 to the focal length f2 of the second lensgroup G2. In the present zoom optical system ZL, successful opticalperformance and a predetermined zoom ratio can be realized by satisfyingthe conditional expression (39).

If the ratio thereof is more than an upper limit of the conditionalexpression (39), refractive power of the second third lens group G2increases, and correction of coma aberration and astigmatism in thewide-angle end state becomes difficult. If the ratio thereof is lessthan a lower limit of the conditional expression (39), refractive powerof the first lens group G1 increases, and correction of coma aberration,astigmatism, and curvature of field in the telephoto end state becomesdifficult.

Further successful aberration correction can be made by setting thelower limit of the conditional expression (39) to 5.30.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (39) to 10.00.

In the zoom optical system ZL according to the sixth embodiment,focusing is preferably made by moving at least a part of the third lensgroup G3 (for example, the biconvex lens L31 in FIG. 22) along theoptical axis direction.

According to this configuration, size reduction of the lens barrel canbe achieved and variations in aberration (for example, sphericalaberration, curvature of field, and the like) upon focusing can besuccessfully corrected.

In the zoom optical system ZL according to the sixth embodiment, thefirst lens group G1 is preferably formed of one cemented lens.

According to this configuration, while size reduction of the lens barrelis achieved, lateral chromatic aberration in the telephoto end state canbe successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, thesecond lens group G2 is preferably formed of two negative lenses and onepositive lens.

According to this configuration, coma aberration and curvature of fieldin the wide-angle end state can be successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, thesecond lens group G2 is preferably formed of, disposed in order from theobject, a negative lens, a negative lens, and a positive lens.

According to this configuration, coma aberration and curvature of fieldin the wide-angle end state can be successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, thethird lens group G3 is preferably formed of six or more lenses.

According to this configuration, spherical aberration and comaaberration can be successfully corrected.

The zoom optical system ZL according to the sixth embodiment preferablysatisfies the following conditional expression (40):30.00°<ωw<80.00°  (40)

where ωw denotes a half angle of view in the wide-angle end state.

The conditional expression (40) represents a condition specifying avalue of an angle of view in the wide-angle end state. While the zoomoptical system ZL has a wide angle of view, coma aberration, distortion,and curvature of field can be successfully corrected by satisfying theconditional expression (40).

Further successful aberration correction can be made by setting thelower limit of the conditional expression (40) to 33.00°. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (40) to 36.00°.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (40) to 77.00°.

The zoom optical system ZL according to the sixth embodiment preferablysatisfies the following conditional expression (41):2.00<ft/fw<15.00  (41)

where ft denotes a focal length of the zoom optical system in thetelephoto end state.

The conditional expression (41) represents a condition specifying aratio of the focal length of the zoom optical system in the telephotoend state to the focal length of the zoom optical system in thewide-angle end state. In the present zoom optical system ZL, a high zoomratio can be obtained, and simultaneously spherical aberration and comaaberration can be successfully corrected by satisfying the conditionalexpression (41).

Further successful aberration correction can be made by setting thelower limit of the conditional expression (41) to 2.30. Still furthersuccessful aberration correction can be made by setting the lower limitof the conditional expression (41) to 2.50. An effect of the sixthembodiment can be exhibited to a maximum by setting the lower limit ofthe conditional expression (41) to 2.70.

Further successful aberration correction can be made by setting theupper limit of the conditional expression (41) to 10.00. Still furthersuccessful aberration correction can be made by setting the upper limitof the conditional expression (41) to 7.00.

According to the sixth embodiment as described above, the zoom opticalsystem ZL having successful optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoomoptical system ZL will be described with reference to FIG. 34. Thecamera 1 is identical with the camera 1 in the fifth embodiment, and theconfiguration has been already described above, and therefore thedescription herein is omitted.

As is known also from each Example described later, the zoom opticalsystem ZL according to the sixth embodiment, mounted in the camera 1 asan imaging lens 2, has successful optical performance by thecharacteristic lens configuration. Thus, according to the present camera1, the imaging device having successful optical performance can berealized.

In addition, even when the above-mentioned zoom optical system ZL ismounted on a single-lens reflex camera that has a quick return mirrorand observes the subject by a finder optical system, an effect similarto the effect of the camera 1 can be produced. Moreover, even when theabove-mentioned zoom optical system ZL is mounted on a video camera, aneffect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZLhaving the configuration will be generally described with reference toFIG. 36. First, each lens is arranged within a lens barrel in such amanner that a zoom optical system ZL has, disposed in order from anobject, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, and a third lens groupG3 having positive refractive power (step ST610). At this time, at leasta part of the third lens group G3 is configured to be movable, as avibration-proof lens group for correcting an image blur, so as to have acomponent in a direction perpendicular to an optical axis (step ST620).Each lens is arranged within the lens barrel in such a manner that atleast the following conditional expression (36) is satisfied among theconditional expressions (step ST630):0.60<f3/fw<3.50  (36)

where f3 denotes a focal length of the third lens group G3, and

fw denotes a focal length of the zoom optical system in the wide-angleend state.

To take a lens arrangement according to the sixth embodiment as oneexample, as shown in FIG. 22, as a first lens group G1, in order from anobject, a cemented positive lens formed by cementing a negative meniscuslens L11 having a convex surface facing the object and a biconvex lensL12 is arranged. As a second lens group G2, in order from the object, anegative meniscus lens L21 having a convex surface facing the object, abiconcave lens L22, and a positive meniscus lens L23 having a convexsurface facing the object are arranged. As a third lens group G3, inorder from the object, a biconvex lens L31, a cemented positive lensformed by cementing a biconvex lens L32 and a biconcave lens L33, apositive meniscus lens L34 having a convex surface facing the object, abiconvex lens L35, and a negative meniscus lens L36 having a convexsurface facing the image are arranged. Moreover, each lens is arrangedin such a manner that the conditional expression (36) (a correspondingvalue of the conditional expression (36) is 1.14) is satisfied.

According to the method for manufacturing the zoom optical systemrelated to the sixth embodiment as described above, the zoom opticalsystem ZL having successful optical performance can be obtained.

Examples According to Fifth and Sixth Embodiments

Next, each Example according to each of the fifth and sixth embodimentswill be described based on drawings. Tables 5 to 7 are provided below,and these Tables show each of specifications in Examples 5 to 7.

FIG. 22, FIG. 26, and FIG. 30 each are a cross-sectional view showing aconfiguration of each of zoom optical systems ZL (ZL5 to ZL7) accordingto each Example. In the cross-sectional view of each of the zoom opticalsystems ZL5 to ZL7, a movement track of each of the lens groups G1 to G3along the optical axis upon zooming from a wide-angle end state (W) to atelephoto end state (T) is shown by an arrow.

Each reference sign for FIG. 22 according to Example 5 is independentlyused for each Example in order to avoid complication of the descriptionby an increase in digit number of the reference sign. Therefore, even ifreference signs common to reference signs in drawings according to otherExamples are placed, the reference signs do not necessarily provideconfigurations common to the configurations in other Examples.

In each Example, ad-line (wavelength: 587.5620nm) and a g-line(wavelength: 435.8350 nm) are selected as an object for calculation ofaberration characteristics.

In “Lens Data” in the Table, a surface number indicates an order ofoptical surfaces from the object along a direction in which a ray oflight progresses, r denotes a radius of curvature of each opticalsurface, D denotes a distance to the next lens surface being thedistance on an optical axis from each optical surface to the nextoptical surface (or image surface), υd denotes the Abbe number of amaterial of an optical member on the basis of the d-line, and nd denotesa refractive index for the d-line of the material of the optical member.Moreover, (Variable) indicates a variable distance to the next lenssurface, “∞” in a radius of curvature indicates a flat surface or anaperture, and (Stop S) indicates an aperture stop S. A refractive index(d-line) of air “1.00000” is omitted. When the optical surface isaspherical, “*” is placed on a left side of the surface number, and aparaxial radius of curvature is shown in a column of the radius ofcurvature r.

In “Aspherical Surface Data” in the Table, a shape of an asphericalsurface shown in “Lens Data” is expressed by the following expression(b). Here, y denotes a height in a direction perpendicular to an opticalaxis, X(y) denotes an amount of displacement (amount of sag) in anoptical axis direction at a height y, r denotes a radius of curvature(paraxial radius of curvature) of a reference spherical surface, xdenotes a conical coefficient, and An represents an n-th asphericalcoefficient. In addition, “E-n” represents “×10^(−n),” and for example,“1.234E-05” represents “1.234×10⁻⁵.”X(y)=(y ² /r)/[1+{1−κ(y ² /r ²)}^(1/2)]+A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y¹⁰  (b)

In “Various Data” in the Table, f denotes a focal length of a whole lenssystem, Fno denotes an F-number, ω denotes a half angle of view (a unit:°), Y denotes an image height, TL denotes a total length of a lenssystem (a distance from a lens forefront surface to an image surface Ion an optical axis), and Bf denotes a back focus (a distance from a lensfinal surface to the image surface I on the optical axis).

In “Variable Distance Data” in the Table, a focal length f or imagingmagnification β of a zoom optical system in a wide-angle end state, anintermediate focal length state, and a telephoto end state upon focusingon infinity and a short distant object (an imaging distance R=2.0 m),and a value of each variable distance is shown. In addition, D0 denotesa distance from an object surface to a first surface, and Di (where, iis an integer) denotes a variable distance between an i-th surface and a(i+1)-th surface.

In “Lens Group Data” in the Table, a start surface number (surfacenumber on a side closest to the object) of each group is shown in agroup first surface, and a focal length of each group is shown in agroup focal length.

In “Conditional Expression Corresponding Value” in the Table, valuescorresponding to the conditional expressions (30) to (41) are shown.

In the following, in all the values of the specifications, unlessotherwise stated, “mm” is generally used for the focal length f, theradius of curvature r, the distance to the next lens surface D and otherlengths, and the like entered therein. However, equivalent opticalperformance can be obtained even if the optical system is proportionallyscaled up or scaled down, and therefore the values are not limitedthereto. Moreover, the unit is not limited to “mm,” and otherappropriate units can be used.

The description with regard to Table so far is common in all Examples,and the description in the following is omitted.

(Example 5)

Example 5 will be described using FIG. 22, FIGS. 23A-23C, 24A-24C,25A-25C and Table 5. As shown in FIG. 22, a zoom optical system ZL (ZL5)according to Example 5 is configured of, disposed in order from anobject along an optical axis, a first lens group G1 having positiverefractive power, a second lens group G2 having negative refractivepower, and a third lens group G3 having positive refractive power.

The first lens group G1 is formed of, disposed in order from the object,a cemented positive lens formed by cementing a negative meniscus lensL11 having a convex surface facing the object and a biconvex lens L12.

The second lens group G2 is formed of, disposed in order from theobject, a negative meniscus lens L21 having a convex surface facing theobject, a biconcave lens L22, and a positive meniscus lens L23 having aconvex surface facing the object. A surface of the negative meniscuslens L21 to the object is aspherical.

The third lens group G3 is formed of, disposed in order from the object,a biconvex lens L31, a cemented positive lens formed by cementing abiconvex lens L32 and a biconcave lens L33, a positive meniscus lens L34having a convex surface facing the object, a biconvex lens L35, and anegative meniscus lens L36 having a convex surface facing an image.

An aperture stop S determining an F-number is provided within the thirdlens group G3.

An image surface I is formed on an imaging element (not shown), and theimaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL5 according to Example 5, zooming from awide-angle end state to a telephoto end state is made by varying an airdistance between the first lens group G1 and the second lens group G2and an air distance between the second lens group G2 and the third lensgroup G3. At this time, relative to the image surface I, the first lensgroup G1 to the third lens group G3 move to the object. The aperturestop S moves to the object integrally with the third lens group G3 uponzooming.

More specifically, in the zoom optical system ZL5 according to Example5, zooming from the wide-angle end state to the telephoto end state ismade by moving each of the lens groups G1 to G3 along the optical axisin such a manner that the air distance between the first lens group G1and the second lens group G2 is enlarged, and the air distance betweenthe second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL5 according to Example 5 has a configurationin which focusing is made by moving the biconvex lens L31, in the thirdlens group G3, along the optical axis direction, and as shown by anarrow in FIG. 22, upon causing a change from a state of focusing oninfinity to a state of focusing on a short distant object, the biconvexlens L31 moves from the object to the image.

Upon occurrence of an image blur, correction of the image blur(vibration proofing) on the image surface I is made by moving, as avibration-proof lens group, the positive meniscus lens L34 having theconvex surface facing the object in the third lens group G3 so as tohave a component in a direction perpendicular to the optical axis.

Table 5 below shows values of each of specifications in Example 5.Surface numbers 1 to 21 in Table 5 correspond to optical surfaces m1 tom21 shown in FIG. 22, respectively.

TABLE 5 [Lens Data] Surface Number r D νd nd  1 73.1346 1.6000 23.801.84666  2 47.7461 4.4680 55.52 1.69680  3 −2795.9453 D3 (Variable) *486.1349 1.3000 46.60 1.80400  5 11.7958 6.0000  6 −86.9238 1.0000 46.601.80400  7 38.6168 0.1000  8 20.8772 3.0000 23.80 1.84666  9 111.9344 D9(Variable) 10 32.7034 2.2000 55.35 1.67790 11 −64.0118 D11 (Variable) 12 ∞ 0.5000 (Stop S) 13 9.7190 3.1000 61.22 1.58913 14 −45.7099 1.104429.37 1.95000 15 14.5899 5.0000 16 30.0000 1.5000 31.27 1.90366 17200.0000 3.0000 18 296.9316 2.1000 50.27 1.71999 19 −22.1475 1.6841 20−9.9417 1.1000 46.60 1.80400 21 −24.7454 Bf (Variable) [AsphericalSurface Data] The 4th Surface K = 1.0000 A4 = −1.68932E−06 A6 =3.45601E−09 A8 = 3.25066E−11 A10 = −1.38349E−13 [Various Data] f18.50~53.50 Fno 3.62~5.91 ω 39.30~14.42 Y 14.25~14.25 TL  80.892~108.569Bf 18.519~37.340 [Variable Distance Data] (Infinity) (Imaging Distance 2m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End EndIntermediate End f, β 18.503 34.953 53.500 −0.009 −0.018 −0.027 D0 0.0000.000 0.000 1918.427 1909.008 1890.749 D3 1.000 9.986 25.233 1.000 9.98625.233 D9 17.878 6.525 2.500 18.261 6.878 3.013  D11 4.739 4.739 4.7394.356 4.387 4.226 Bf 18.519 30.304 37.340 18.519 30.304 37.340 [LensGroup Data] Group Group First Group Focal Number Surface Length G1 1114.802 G2 4 −18.462 G3 10 21.087 [Conditional Expression CorrespondingValue] Conditional Expression (30): f3/fw = 1.14 Conditional Expression(31): f1/f3 = 5.44 Conditional Expression (32): f2/(−f3) = 0.88Conditional Expression (33): f1/(−f2) = 6.22 Conditional Expression(34): ωw = 39.30 Conditional Expression (35): ft/fw = 2.89 ConditionalExpression (36): f3/fw = 1.14 Conditional Expression (37): f1/f3 = 5.44Conditional Expression (38): f2/(−f3) = 0.88 Conditional Expression(39): f1/(−f2) = 6.22 Conditional Expression (40): ωw = 39.30Conditional Expression (41): ft/fw = 2.89

Table 5 shows that the zoom optical system ZL5 according to Example 5satisfies the conditional expressions (30) to (41).

FIGS. 23A, 23B and 23C are graphs showing aberrations of the zoomoptical system ZL5 according to Example 5 in a wide-angle end state(f=18.50), in which FIG. 23A is graphs showing various aberrations uponfocusing on infinity, FIG. 23B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 23C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.009). FIGS. 24A, 24B and 24C are graphs showingaberrations of the zoom optical system ZL5 according to Example 5 in anintermediate focal length state (f=34.95), in which FIG. 24A is graphsshowing various aberrations upon focusing on infinity, FIG. 24B isgraphs showing coma aberration when an image blur is corrected (avibration-proof lens group shift amount=0.2 mm) upon focusing oninfinity, and FIG. 24C is graphs showing various aberrations uponfocusing on a short distant object (imaging magnification β=−0.018).FIGS. 25A, 25B and 25C are graphs showing aberrations of the zoomoptical system ZL5 according to Example 5 in a telephoto end state(f=53.50), in which FIG. 25A is graphs showing various aberrations uponfocusing on infinity, FIG. 25B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 25C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.027). In the present Example, as shown in FIG. 23B,FIG. 24B, and FIG. 25B, optical performance upon vibration proofing isshown in graphs showing coma aberration, centering on an image heighty=0.0, corresponding to image heights of vertically plus 10.0 and minus10.0.

In each graph showing aberration, FNO denotes an F-number, Y denotes animage height, d denotes aberration in a d-line, and g denotes aberrationin a g-line. A column without description of d or g indicates aberrationin the d-line. In the graphs showing spherical aberration, a value ofthe F-number corresponding to a maximum aperture is shown, and in thegraphs showing astigmatism and distortion, a maximum value of the imageheight is shown. In the graphs showing astigmatism, a solid lineindicates a sagittal image surface and a broken line indicates ameridional image surface. In the graphs showing coma aberration, a solidline indicates meridional coma, and a broken line indicates sagittalcoma. The description of the graphs showing aberration above is regardedto be the same also in other Examples, and the description thereof isomitted.

From each of the graphs showing aberration shown in FIGS. 23A-23C,24A-24C and 25A-25C, the zoom optical system ZL5 according to Example 5is found to have high imaging performance in which various aberrationsare successfully corrected from the wide-angle end state to thetelephoto end state. Moreover, the zoom optical system ZL5 is found tohave high imaging performance also upon correcting the image blur.

(Example 6)

Example 6 will be described using FIG. 26, FIGS. 27A-27C, 28A-28C,29A-29C and Table 6. As shown in FIG. 26, a zoom optical system ZL (ZL6)according to Example 6 is configured of, disposed in order from anobject along an optical axis, a first lens group G1 having positiverefractive power, a second lens group G2 having negative refractivepower, and a third lens group G3 having positive refractive power.

The first lens group G1 is formed of, disposed in order from the object,a cemented positive lens formed by cementing a negative meniscus lensL11 and a positive meniscus lens L12 each having a convex surface facingthe object.

The second lens group G2 is formed of, disposed in order from theobject, a negative meniscus lens L21 having a convex surface facing theobject, a biconcave lens L22, and a positive meniscus lens L23 having aconvex surface facing the object. A surface of the negative meniscuslens L21 to the object is aspherical.

The third lens group G3 is formed of, disposed in order from the object,a positive meniscus lens L31 having a convex surface facing the object,a cemented positive lens formed by cementing a biconvex lens L32 and anegative meniscus lens L33, a negative meniscus lens L34 having a convexsurface facing the object, a biconvex lens L35, and a negative meniscuslens L36 having a convex surface facing an image. A surface of thenegative meniscus lens L36 to the image is aspherical.

An aperture stop S determining an F-number is provided within the thirdlens group G3.

An image surface I is formed on an imaging element (not shown), and theimaging element is formed of a CCD or a CMOS, for example.

In the zoom optical system ZL6 according to Example 6, zooming from awide-angle end state to a telephoto end state is made by varying an airdistance between the first lens group G1 and the second lens group G2and an air distance between the second lens group G2 and the third lensgroup G3. At this time, relative to the image surface I, the first lensgroup G1 to the third lens group G3 move to the object. The aperturestop S moves to the object integrally with the third lens group G3 uponzooming.

More specifically, in the zoom optical system ZL6 according to Example6, zooming from the wide-angle end state to the telephoto end state ismade by moving each of the lens groups G1 to G3 along the optical axisin such a manner that the air distance between the first lens group G1and the second lens group G2 is enlarged, and the air distance betweenthe second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL6 according to Example 6 has a configurationin which focusing is made by moving the positive meniscus lens L31having the convex surface facing the object, in the third lens group G3,along the optical axis direction, and as shown by an arrow in FIG. 26,upon causing a change from a state of focusing on infinity to a state offocusing on a short distant object, the positive meniscus lens L31 movesfrom the object to the image.

Upon occurrence of an image blur, correction of the image blur(vibration proofing) on the image surface I is made by moving, as avibration-proof lens group, the negative positive meniscus lens L34having the convex surface facing the object in the third lens group G3so as to have a component in a direction perpendicular to the opticalaxis.

Table 6 below shows values of each of specifications in Example 6.Surface numbers 1 to 21 in Table 6 correspond to optical surfaces m1 tom21 shown in FIG. 26.

TABLE 6 [Lens Data] Surface Number r D νd nd  1 53.5681 1.6000 23.801.84666  2 37.0346 5.7211 55.52 1.69680  3 353.3821 D3 (Variable) *445.0000 1.2492 46.60 1.80400  5 12.0000 4.6255  6 −419.8499 1.0000 46.601.80400  7 16.0327 2.2223  8 17.7685 3.0523 23.80 1.84666  9 54.0639 D9(Variable) 10 30.8461 2.0203 55.52 1.69680 11 1697.1702 D11 (Variable) 12 ∞ 0.5000 (Stop S) 13 15.5855 3.7128 63.88 1.51680 14 −13.3636 1.012127.57 1.75520 15 −31.5468 4.5348 16 52.8796 1.0000 29.37 1.95000 1726.1372 4.8969 18 23.6866 2.7133 46.97 1.54072 19 −63.5925 1.9047 20−10.9032 1.5000 46.60 1.80400 *21  −19.7349 Bf (Variable) [AsphericalSurface Data] The 4th Surface K = 1.0000 A4 = −5.26610E−06 A6 =−3.69410E−08 A8 = 1.17750E−10 A10 = −9.98120E−14 The 21st Surface K =1.0000 A4 = 2.90520E−05 A6 = −1.19970E−08 A8 = −6.98280E−10 A10 =0.00000E+00 [Various Data] f 18.74~52.08 Fno 3.77~5.71 ω 39.16~14.81 Y14.25~14.25 TL  79.523~109.107 Bf 18.021~35.053 [Variable Distance Data](Infinity) (Imaging Distance 2 m) Wide-Angle Telephoto Wide-AngleTelephoto End Intermediate End End Intermediate End f, β 18.741 34.49652.082 −0.010 −0.018 −0.026 D0 0.000 0.000 0.000 1919.796 1906.9501890.212 D3 1.546 11.351 25.190 1.546 11.351 25.190 D9 13.592 5.4822.500 13.794 5.765 2.958  D11 3.099 3.099 3.099 2.897 2.816 2.641 Bf18.021 29.172 35.053 18.021 29.172 35.053 [Lens Group Data] Group GroupFirst Group Focal Number Surface Length G1 1 100.52307 G2 4 −15.10823 G310 19.34026 [Conditional Expression Corresponding Value] ConditionalExpression (30): f3/fw = 1.03 Conditional Expression (31): f1/f3 = 5.20Conditional Expression (32): f2/(−f3) = 0.78 Conditional Expression(33): f1/(−f2) = 6.65 Conditional Expression (34): ωw = 39.16Conditional Expression (35): ft/fw = 2.78 Conditional Expression (36):f3/fw = 1.03 Conditional Expression (37): f1/f3 = 5.20 ConditionalExpression (38): f2/(−f3) = 0.78 Conditional Expression (39): f1/(−f2) =6.65 Conditional Expression (40): ωw = 39.16 Conditional Expression(41): ft/fw = 2.78

Table 6 shows that the zoom optical system ZL6 according to Example 6satisfies the conditional expressions (30) to (41).

FIGS. 27A, 27B and 27C are graphs showing aberrations of the zoomoptical system ZL6 according to Example 6 in a wide-angle end state(f=18.74), in which FIG. 27A is graphs showing various aberrations uponfocusing on infinity, FIG. 27B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 27C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.010). FIGS. 28A, 28B and 28C are graphs showingaberrations of the zoom optical system ZL6 according to Example 6 in anintermediate focal length state (f=34.50), in which FIG. 28A is graphsshowing various aberrations upon focusing on infinity, FIG. 28B isgraphs showing coma aberration when an image blur is corrected (avibration-proof lens group shift amount=0.2 mm) upon focusing oninfinity, and FIG. 28C is graphs showing various aberrations uponfocusing on a short distant object (imaging magnification β=−0.018).FIGS. 29A, 29B and 29C are graphs showing aberrations of the zoomoptical system ZL6 according to Example 6 in a telephoto end state(f=52.08), in which FIG. 29A is graphs showing various aberrations uponfocusing on infinity, FIG. 29B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 29C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.026).

From each of the graphs showing aberration shown in FIGS. 27A-27C,28A-28C and 29A-29C, the zoom optical system ZL6 according to Example 6is found to have high imaging performance in which various aberrationsare successfully corrected from the wide-angle end state to thetelephoto end state. Moreover, the zoom optical system ZL6 is found tohave high imaging performance also upon correcting the image blur.

(Example 7)

Example 7 will be described using FIG. 30 to FIGS. 31A-31C, 32A-32C,33A-33C and Table 7. As shown in FIG. 30, a zoom optical system ZL (ZL7)according to Example 7 is configured of, disposed in order from anobject along an optical axis, a first lens group G1 having positiverefractive power, a second lens group G2 having negative refractivepower, and a third lens group G3 having positive refractive power.

The first lens group G1 is formed of, disposed in order from the object,a cemented positive lens formed by cementing a negative meniscus lensL11 having a convex surface facing the object and a biconvex lens L12.

The second lens group G2 is formed of, disposed in order from theobject, a negative meniscus lens L21 having a convex surface facing theobject, a biconcave lens L22, and a positive meniscus lens L23 having aconvex surface facing the object. A surface of the negative meniscuslens L21 to the object is aspherical.

The third lens group G3 is formed of, disposed in order from the object,a positive meniscus lens L31 having a convex surface facing the object,a cemented positive lens formed by cementing a biconvex lens L32 and anegative meniscus lens L33 having a convex surface facing an image, abiconvex lens L34, and a biconcave lens L35. A surface of the negativemeniscus lens L34 to the image is aspherical.

An aperture stop S determining an F-number is provided within the thirdlens group G3.

An image surface I is formed on an imaging element (not shown), and theimaging element is formed of a CCD or a CMOS, for example.

In the zoom optical system ZL7 according to Example 7, zooming from awide-angle end state to a telephoto end state is made by varying an airdistance between the first lens group G1 and the second lens group G2and an air distance between the second lens group G2 and the third lensgroup G3. At this time, relative to the image surface I, the first lensgroup G1 to the third lens group G3 move to the object. The aperturestop S moves to the object integrally with the third lens group G3 uponzooming.

More specifically, in the zoom optical system ZL7 according to Example7, zooming from the wide-angle end state to the telephoto end state ismade by moving each of the lens groups G1 to G3 along the optical axisin such a manner that the air distance between the first lens group G1and the second lens group G2 is enlarged, and the air distance betweenthe second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL7 according to Example 7 has a configurationin which focusing is made by moving the biconvex lens L34 of the thirdlens group G3 along an optical axis direction, and as shown by an arrowin FIG. 30, upon causing a change from a state of focusing on infinityto a state of focusing on a short distant object, the biconvex lens L34moves from the object to the image.

Upon occurrence of an image blur, correction of the image blur(vibration proofing) on the image surface I is made by moving, as avibration-proof lens group, the positive meniscus lens L31 having theconvex surface facing the image in the third lens group G3 so as to havea component in a direction perpendicular to the optical axis.

Table 7 below shows values of each of specifications in Example 7.Surface numbers 1 to 19 in Table 7 correspond to optical surfaces m1 tom19 shown in FIG. 30.

TABLE 7 [Lens Data] Surface Number r D νd nd  1 53.2376 1.6000 23.801.84666  2 38.1514 6.3571 63.34 1.61800  3 −369.5355 D3 (Variable) *437.0679 1.2789 52.34 1.75500  5 11.0000 5.1524  6 −55.1564 1.0000 46.601.80400  7 24.6508 0.5019  8 17.1923 3.0456 23.80 1.84666  9 55.8429 D9(Variable) 10 −147.8871 1.8235 59.42 1.58313 11 −38.8546 0.9660 12 ∞0.4673 (Stop S) 13 13.2618 3.3759 65.44 1.60300 14 −18.1264 1.0943 29.371.95000 15 −141.8073 D15 (Variable)  16 32.4435 1.9144 49.62 1.77250*17  −28.4962 D17 (Variable)  18 −19.1230 1.1000 46.59 1.81600 1955.1349 Bf (Variable) [Aspherical Surface Data] The 4th Surface K =1.0000 A4 = −2.53250E−05 A6 = −1.03610E−07 A8 = 7.17390E−10 A10 =−2.12490E−12 The 17th Surface K = 1.0000 A4 = 7.38500E−05 A6 =4.27730E−07 A8 = 0.00000E+00 A10 = 0.00000E+00 [Various Data] f18.72~52.00 Fno 3.60~5.57 ω 39.22~14.29 Y 14.25~14.25 TL 74.332~95.718Bf 18.038~32.068 [Variable Distance Data] (Infinity) (Imaging Distance 2m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End EndIntermediate End f, β 18.724 35.500 52.000 −0.010 −0.018 −0.027 D0 0.0000.000 0.000 1924.987 1912.247 1903.600 D3 1.000 14.288 20.264 1.00014.288 20.264 D9 13.907 5.856 2.000 13.907 5.856 2.000  D15 8.710 8.7108.710 8.661 8.597 8.533  D17 3.000 3.000 3.000 3.049 3.112 3.177 Bf18.038 25.541 32.068 18.038 25.541 32.068 [Lens Group Data] Group GroupFirst Group Focal Number Surface Length G1 1 86.38416 G2 4 −15.99559 G310 17.86718 [Conditional Expression Corresponding Value] ConditionalExpression (30): f3/fw = 0.95 Conditional Expression (31): f1/f3 = 4.83Conditional Expression (32): f2/(−f3) = 0.90 Conditional Expression(33): f1/(−f2) = 5.40 Conditional Expression (34): ωw = 39.22Conditional Expression (35): ft/fw = 2.78 Conditional Expression (36):f3/fw = 0.95 Conditional Expression (37): f1/f3 = 4.83 ConditionalExpression (38): f2/(−f3) = 0.90 Conditional Expression (39): f1/(−f2) =5.40 Conditional Expression (40): ωw = 39.22 Conditional Expression(41): ft/fw = 2.78

Table 7 shows that the zoom optical system ZL7 according to Example 7satisfies the conditional expressions (30) to (41).

FIGS. 31A, 31B and 31C are graphs showing aberrations of the zoomoptical system ZL7 according to Example 7 in a wide-angle end state(f=18.72), in which FIG. 31A is graphs showing various aberrations uponfocusing on infinity, FIG. 31B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount=0.2mm) upon focusing on infinity, and FIG. 31C is graphs showing variousaberrations upon focusing on a short distant object (imagingmagnification β=−0.010). FIGS. 32A, 32B and 32C are graphs showingaberrations of the zoom optical system ZL7 according to Example 7 in anintermediate focal length state (f=35.50), in which FIG. 32A is graphsshowing various aberrations upon focusing on infinity, FIG. 32B isgraphs showing coma aberration when an image blur is corrected (avibration-proof lens group shift amount=0.2 mm) upon focusing oninfinity, and FIG. 32C is graphs showing various aberrations uponfocusing on a short distant object (imaging magnification β=−0.018).FIGS. 33A, 33B and 33C are graphs showing aberrations of the zoomoptical system ZL7 according to Example 7 in a telephoto end state(f=52.00), in which FIG. 33A is graphs showing various aberrations uponfocusing on infinity, FIG. 33B is graphs showing coma aberration when animage blur is corrected (a vibration-proof lens group shift amount of0.2 mm) upon focusing on infinity, and FIG. 33C is graphs showingvarious aberrations upon focusing on a short distant object (imagingmagnification β=−0.027).

From each of the graphs showing aberration shown in FIGS. 31A-31C,32A-32C and 33A-33C, the zoom optical system ZL7 according to Example 7is found to have high imaging performance in which various aberrationsare successfully corrected from the wide-angle end state to thetelephoto end state. Moreover, the zoom optical system ZL7 is found tohave high imaging performance also upon correcting the image blur.

According to each Example described above, the zoom optical systemhaving successful optical performance can be realized.

In addition, each Example described above shows one specific example ofthe zoom optical system according to each of the fifth and sixthembodiments, and the zoom optical systems according to the fifth andsixth embodiments are not limited thereto. In the fifth and sixthembodiments, the following content can be appropriately adopted withinthe range in which the optical performance is not adversely affected.

In Examples using numerical values according to the fifth and sixthembodiments, a three-group configuration was shown. However, the presentinvention can also be applied to other configurations such as afour-group configuration. For example, a configuration is allowed inwhich a lens or lens group is added thereto on a side closest to theobject, or a configuration in which a lens or lens group is addedthereto on a side closest to the image. Moreover, the lens grouprepresents a part which is separated by the air distance which changesupon zooming or focusing and has at least one lens.

In the fifth and sixth embodiments, the zoom optical system may beformed into a focusing lens group in which focusing on an infinitedistant object to a short distant object is made by moving a single lensgroup or a plurality of lens groups, or a partial lens group in theoptical axis direction. The focusing lens group can also be applied toautofocusing, and is also suitable for a motor drive (using anultrasonic motor, or the like) for autofocusing. In particular, at leasta part of the third lens group G3 is preferably applied as the focusinglens group.

In the fifth and sixth embodiments, the zoom optical system may beformed into the vibration-proof lens group in which the image blurcaused by camera shake is corrected by moving the lens group or thepartial lens group so as to have the component in the directionperpendicular to the optical axis, or rotationally moving (swinging) thelens group or the partial lens group in an in-plane direction includingthe optical axis. In particular, at least a part of the third lens groupG3 is preferably applied as the vibration-proof lens group.

In the fifth and sixth embodiments, a lens surface may be formed of aspherical surface or a flat surface, or formed of an aspherical surface.When the lens surface is spherical or flat, lens processing and assemblyand adjustment are facilitated, and deterioration of optical performanceby an error of the processing and assembly and adjustment can beprevented, and such a case is preferable. Moreover, when the lenssurface is aspherical, the aspherical surface may be any asphericalsurface, including an aspherical surface by grinding, a glass moldaspherical surface in which glass is formed into an aspherical surfaceshape by using a mold, and a composite type aspherical surface in whicha resin is formed into the aspherical surface shape on a surface ofglass. Moreover, the lens surface may be formed into a diffractionsurface, or the lens may be formed into a gradient index lens (GRINlens) or a plastic lens.

In the fifth and sixth embodiments, the aperture stop S is preferablyarranged in a neighborhood of the third lens group G3 or within thethird lens group G3. However, a lens frame may be used as substitutionfor such a role without providing a member as the aperture stop.

In the fifth and sixth embodiments, an antireflection film having hightransmittance in a wide wavelength range may be applied to each lenssurface in order to reduce a flare and a ghost to achieve high opticalperformance with high contrast.

The zoom optical systems ZL according to the fifth and sixth embodimentseach have a zoom ratio of about 2 to 7.

EXPLANATION OF NUMERALS AND CHARACTERS

ZL (ZL1 to ZL7) Zoom optical system

G1 First lens group

G2 Second lens group

G3 Third lens group

S Aperture stop

I Image surface

1 Camera (imaging device)

2 Imaging lens (zoom optical system)

The invention claimed is:
 1. A zoom optical system, comprising: in orderfrom an object, a first lens group having positive refractive power; asecond lens group having negative refractive power; and a third lensgroup having positive refractive power, wherein upon zooming from awide-angle end state to a telephoto end state, the first lens group ismoved toward the object along an optical axis, focusing is effected bymoving at least a part of the third lens group along the optical axis,the third lens group comprises, in order from the object, a 3A lensgroup and a 3B lens group each having positive refractive power, atleast a part of the 3B lens group is configured to be movable, as avibration-proofing lens group for correcting an image blur, so as tohave a movement component in a direction perpendicular to the opticalaxis, and the following conditional expressions are satisfied:0.73<(−f2)/f3<2.002.00<|fvr|/f3<6.00 where f2 denotes a focal length of the second lensgroup, f3 denotes a focal length of the third lens group, and fvrdenotes a focal length of the vibration-proofing lens group.
 2. The zoomoptical system according to claim 1, wherein, the 3A lens group is movedalong the optical axis during focusing.
 3. The zoom optical systemaccording to claim 2, wherein the following conditional expression issatisfied:1.00<f3A/f3<4.00 where f3A denotes a focal length of the 3A lens group.4. The zoom optical system according to claim 2, wherein the 3A lensgroup consists of a single lens.
 5. The zoom optical system according toclaim 2, wherein the following conditional expression is satisfied:1.00<f3B/f3<5.00 where f3B denotes a focal length of the 3B lens group.6. The zoom optical system according to claim 2, wherein thevibration-proofing lens group has negative refractive power.
 7. The zoomoptical system according to claim 2, wherein the vibration-proofing lensgroup consists of a single lens.
 8. An imaging device, comprising thezoom optical system according to claim
 1. 9. A method for manufacturinga zoom optical system, comprising: disposing, in order from an object, afirst lens group having positive refractive power, a second lens grouphaving negative refractive power, and a third lens group having positiverefractive power, wherein the lens groups are arranged within a lensbarrel in such a manner that, upon zooming from a wide-angle end stateto a telephoto end state, the first lens group is moved toward theobject along an optical axis, focusing is effected by moving at least apart of the third lens group along the optical axis, the third lensgroup comprises, in order from the object, a 3A lens group and a 3B lensgroup each having positive refractive power, at least a part of the 3Blens group is configured to be movable, as a vibration-proofing lensgroup for correcting an image blur, so as to have a movement componentin a direction perpendicular to the optical axis, and the followingconditional expressions are satisfied:0.73<(−f2)/f3<2.002.00<|fvr|/f3<6.00 where f2 denotes a focal length of the second lensgroup, f3denotes a focal length of the third lens group, and fvr denotesa focal length of the vibration-proofing lens group.
 10. A zoom opticalsystem, comprising: in order from an object, a first lens group havingpositive refractive power; a second lens group having negativerefractive power; and a third lens group having positive refractivepower, wherein focusing is effected by moving, at least a part of thethird lens group, as a focusing lens group, along an optical axis, thethird lens group comprises six or more lenses, and the followingconditional expressions are satisfied:0.90<f3/fw<1.504.70<f1/f3<10.00 where f3denotes a focal length of the third lens group,fw denotes a focal length of the zoom optical system in a wide-angle endstate, and f1 denotes a focal length of the first lens group.
 11. Thezoom optical system according to claim 10, wherein zooming is effectedby varying an air distance between the first lens group and the secondlens group and an air distance between the second lens group and thethird lens group.
 12. The zoom optical system according to claim 10,wherein, upon zooming from the wide-angle end state to a telephoto endstate, an air distance between the first lens group and the second lensgroup is increased, and an air distance between the second lens groupand the third lens group is decreased.
 13. The zoom optical systemaccording to claim 10, wherein the following conditional expression issatisfied:0.60<(−f2)/f3<1.05 where f2 denotes a focal length of the second lensgroup.
 14. The zoom optical system according to claim 10, wherein thefollowing conditional expression is satisfied:5.20<f1/(−f2)<30.00 where f1 denotes a focal length of the first lensgroup, and f2 denotes a focal length of the second lens group.
 15. Thezoom optical system according to claim 10, wherein at least a part ofthe third lens group is configured to be movable, as avibration-proofing lens group for correcting an image blur, so as tohave a movement component in a direction perpendicular to the opticalaxis.
 16. The zoom optical system according to claim 15, wherein thefocusing lens group is arranged, in the third lens group, so as to becloser than the vibration-proofing lens group to the object.
 17. Thezoom optical system according to claim 16, wherein the focusing lensgroup is arranged closest to the object in the third lens group.
 18. Thezoom optical system according to claim 16, wherein the focusing lensgroup consists of a single lens.
 19. The zoom optical system accordingto claim 15, wherein the vibration-proofing lens group is arranged, inthe third lens group, so as to be closer than the focusing lens group tothe object.
 20. The zoom optical system according to claim 19, whereinthe vibration-proofing lens group is arranged closest to the object inthe third lens group.
 21. The zoom optical system according to claim 19,wherein the vibration-proofing lens group consists of a single lens. 22.The zoom optical system according to claim 10, wherein the first lensgroup comprises one cemented lens.
 23. The zoom optical system accordingto claim 10, wherein the second lens group comprises two negative lensesand one positive lens.
 24. The zoom optical system according to claim10, wherein the second lens group comprises, in order from the object, anegative lens, a negative lens, and a positive lens.
 25. The zoomoptical system according to claim 10, further comprising: an aperturestop, and wherein the aperture stop is arranged between the second lensgroup and an image surface.
 26. The zoom optical system according toclaim 10, wherein the following conditional expression is satisfied:30.00°<ωw <80.00° where ωw denotes a half angle of view in thewide-angle end state.
 27. The zoom optical system according to claim 10,wherein the following conditional expression is satisfied:2.00<ft/fw<15.00 where ft denotes a focal length of the zoom opticalsystem in a telephoto end state.
 28. An imaging device, comprising thezoom optical system according to claim
 10. 29. A method formanufacturing a zoom optical system, comprising: disposing, in orderfrom an object, a first lens group having positive refractive power, asecond lens group having negative refractive power, and a third lensgroup having positive refractive power, wherein the lens groups arearranged within a lens barrel in such a manner that focusing is effectedby moving at least a part of the third lens group, as a focusing lensgroup, along an optical axis, the third lens group comprises six or morelenses, and the following conditional expressions are satisfied:0.90<f3/fw<1.504.70<f1/f3<10.00 where f3denotes a focal length of the third lens group,fw denotes a focal length of the zoom optical system in a wide-angle endstate, and f1 denotes a focal length of the first lens group.